Used by Tailwind Labs and recognized as an official GitHub funding partner, Polar is the open-source billing infrastructure that lets developers ship production-ready monetization in hours instead of weeks. Meter tokens, API calls, agent runs, GPU seconds, and storage with event-level precision, then compose usage billing with subscriptions, seats, credits, trials, and discounts into whatever pricing model your product requires. As Merchant of Record, Polar handles sales tax, VAT, chargebacks, receipts, and regulatory compliance across all supported countries so you receive clean payouts without building tax infrastructure. Integrate via the full REST API with official SDKs for JavaScript, Python, PHP, and Go, plus framework adapters for Next.js, Astro, Remix, SvelteKit, and Laravel enabling checkout integration in minutes. Automatically deliver benefits upon purchase including GitHub repository access, Discord roles, license keys, file downloads, and meter credits through configurable automation rules. The built-in customer portal provides subscription management, payment method updates, invoice history, and benefit access with full white-label branding. Monitor revenue, costs, and margins through real-time analytics dashboards showing the unit economics every AI startup needs to scale. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache License 2.0 licensed.

Trusted by Mistral AI, PayPal, Groq, and Synthesia with over 10,300 GitHub stars and Y Combinator backing, Lago is the open-source billing engine that handles usage-based, subscription-based, and hybrid pricing models through a single API-first platform — replacing the need to build custom billing logic or depend on opaque SaaS pricing infrastructure. Real-time event ingestion via ClickHouse processes billable events with deduplication and multiple aggregation methods including count, sum, unique count, max, and weighted sum, while graduated pricing tiers, package-based billing, and percentage-based fees model any pricing strategy from simple subscriptions to complex marketplace commission structures. Automated invoice generation calculates charges according to configurable billing cycles with grace periods, proration for mid-cycle changes, and credit note issuance for refunds and adjustments. Prepaid credits enable pay-in-advance models where customers purchase credit blocks and draw down as usage accumulates, while entitlements tie feature access directly to billing plans for automated provisioning and de-provisioning. Payment orchestration integrates natively with Stripe, Adyen, and GoCardless with automatic retry logic, dunning workflows for failed payments, and multi-gateway routing. Revenue analytics provide cross-stream visibility into MRR, usage trends, churn, and revenue drivers through dedicated API endpoints. The customer portal embeds into your application for self-service invoice access and usage monitoring. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Kill Bill handles the complete subscription billing lifecycle from plan definition through invoice generation to payment collection across any gateway, with 15 years of Fortune 500 production use and 5,600+ GitHub stars behind it. Plans, trials, add-ons, and pricing tiers live in a versioned XML catalog that propagates changes without code deploys. The multi-phase subscription engine manages trial periods, promotional discounts, evergreen billing, usage-based metering, and hybrid pricing models with automatic proration on plan upgrades and downgrades. Automated invoice generation calculates charges, applies credits and adjustments, and triggers payment collection through pluggable gateways including Stripe, Adyen, Braintree, PayPal, and CyberSource. The Java plugin framework extends every billing domain with custom logic for tax calculation via Avalara AvaTax or Vertex, fraud detection through Accertify or Feedzai, and ERP integration without modifying the core. The Kaui admin dashboard gives finance and operations teams account management, subscription controls, invoice views, payment configuration, billing timeline visualization, MRR tracking, advanced search, and full audit history with object-level change tracking. Multi-tenancy isolates billing data across thousands of brands with tenant-specific catalogs, payment configs, and RBAC policies. REST APIs expose every operation with webhook notifications for downstream integration. Deploys via Docker Compose on MySQL or PostgreSQL. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

Flexprice is a developer-first billing platform built specifically for AI-native and SaaS companies that need usage-based, credit-based, and hybrid pricing models without building custom billing infrastructure. The metering engine ingests millions of usage events in real time through HTTP APIs or SDK calls, supporting sum, count, unique count, latest value, and multiplier aggregation strategies across custom event schemas like API calls, token counts, compute minutes, and GPU time. Credit management handles prepaid wallets with promotional grants, rollover caps, auto top-ups, and priority-based credit application during invoice generation. The pricing engine supports per-unit, tiered, volume, package, and flat-rate models with per-customer overrides, committed minimums, and enterprise contract terms. Feature entitlements enforce boolean toggles, metered usage limits, and configuration values per plan, enabling applications to gate functionality through simple API checks. Automated invoicing calculates charges from real-time usage data with proration for mid-cycle upgrades and downgrades, generating detailed line items linked to tracked consumption. The architecture separates event ingestion through Kafka from billing computation via Temporal workflow orchestration, allowing each layer to scale independently with ClickHouse handling high-performance usage aggregation. Stripe Connect integration processes payments and manages customer payment methods. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPLv3 licensed.

Meteroid delivers the billing infrastructure that SaaS companies need when Stripe Billing gets too rigid and building in-house gets too expensive. The Rust backend ingests usage events via REST API or Kafka with deduplication by event ID and customer ID, storing time-series data in ClickHouse for sub-second aggregation queries across billions of events. Billable metrics transform raw events — API calls, compute time, tokens, storage, transactions — into accurate charges using configurable aggregation functions, dimensions, and filters without pre-aggregation. The plan builder supports any pricing structure: flat rate, per-unit, tiered graduated, tiered volume, package, and hybrid combinations with multiple price components per plan. Versioned plans enable pricing changes without affecting existing subscribers through grandfathering, while experiments let you A/B test pricing with controlled rollouts. Subscription management handles the full lifecycle — creation, upgrades, downgrades, mid-cycle proration, scheduled changes, and cancellation with configurable grace periods. The TypeScript frontend provides a complete web dashboard for managing customers, plans, subscriptions, invoices, and revenue analytics with MRR tracking, churn analysis, and cohort insights. Automated invoice generation handles complex scenarios including usage-based line items, credits, discounts, and tax calculations with PDF rendering. Stripe Connect integration enables payment collection directly through the platform. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

With nearly 10,000 GitHub stars and over a decade of development since 2013, Invoice Ninja is the most complete source-available invoicing platform for freelancers and small businesses — combining professional invoicing, online payments, expense tracking, and project management in a single self-hosted application. The Laravel API backend powers a React web portal and Flutter native applications for Windows, macOS, Linux, iOS, and Android, delivering a consistent experience across every device. Create professional invoices and quotes with real-time PDF preview, product libraries, custom templates, and automatic tax calculations. Clients receive branded emails and access their dedicated portal at your custom domain to view documents, approve quotes with e-signatures, and pay with one click via Stripe, PayPal, Square, GoCardless, Authorize.net, Braintree, or Mollie. Recurring invoices with auto-billing charge saved payment methods on schedule — weekly, monthly, or annually — with automatic reminders and late fee calculations. The built-in project management suite includes Kanban boards for task organization, billable time tracking with start/stop timers, and vendor expense management with receipt attachments. Bank account synchronization via Yodlee or GoCardless automatically imports transactions for reconciliation. E-invoicing with PEPPOL network integration supports electronic invoicing standards for European and government compliance. Reports cover invoices, expenses, profit and loss, tax summaries, and aged receivables. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Elastic License v2.

InvoicePlane manages the complete freelance and small-business billing cycle — draft quotes, convert them to invoices, automate recurring charges, collect payments through Stripe and PayPal, and generate EU-compliant eInvoice XML for automated processing by accounting systems. Deployed over 100,000 times across 193 countries, the PHP 8.2+ application on CodeIgniter 3 with MySQL or MariaDB handles everything from first estimate to final receipt. EU-compliant eInvoice generation creates machine-readable XML invoices meeting European Union standards since version 1.6.2. Recurring invoices automate periodic billing with configurable controls that pause generation when previous invoices remain unpaid. Online payment integration lets clients pay directly through Stripe, PayPal with Advanced Credit Cards, and Venmo support. The CRM-like client management module stores contact details, notes, custom fields, and complete transaction history per client. Product and task management modules let you build line-item invoices from reusable product catalogs and project tasks. Customizable PDF templates powered by mPDF support branded invoice layouts with QR codes, while email delivery via PHPMailer handles automated sending with configurable SMTP. A guest portal gives clients read-only access to view and pay their outstanding invoices and quotes. Financial reporting tracks revenue, outstanding balances, and payment history. The multi-language interface supports community translations, and multi-currency handles international invoicing. Deploy via Docker Compose with automatic database migrations. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

SolidInvoice ships a complete billing platform as a single FrankenPHP binary — no separate PHP installation, no web server configuration, just one executable that delivers quote-to-invoice conversion, automated recurring billing, Stripe and PayPal payment processing, multi-currency precision arithmetic, and eight render-ready PDF templates out of the box. Maintained since 2012 across 63 releases with 30 contributors, the Symfony 7 and PHP 8.4 backend provides quote creation with one-click conversion to invoices, recurring billing with configurable frequency schedules, and online payment processing through Payum supporting Stripe, PayPal, and additional gateways. Multi-currency support uses real Money objects for precision arithmetic, while multi-tax support handles invoice-level and line-item tax rates with automatic calculation. Client management stores contacts, multiple addresses with map integration, credit balances, and complete quote and invoice history per client. The redesigned Tabler-based UI features a dashboard with hero statistics, ChartJS revenue trend visualization, attention-required alerts for overdue and draft invoices, quick actions, and a recent activity timeline. A RESTful API enables integrations with external systems. Multi-channel notifications deliver alerts via email, SMS, and webhooks. Google OAuth and two-factor authentication secure access. Grid export and full company data export support backup and migration. Deploy using Docker, Homebrew, the standalone FrankenPHP binary, or from source. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Akaunting is an online accounting software for small businesses and freelancers. The double-entry accounting engine provides a full Chart of Accounts, journal entries, and balance sheet reporting, eliminating the manual errors inherent in single-entry systems. Unlimited invoice creation with customizable templates, automatic payment reminders, and client portal access lets businesses present professional documents and accept payments through PayPal, Stripe, and other gateway integrations. Expense tracking captures operational costs with category-based organization, receipt scanning, and vendor bill management with overdue payment alerts. Bank Feeds auto-syncs transactions from connected bank accounts and matches them against invoices and bills for streamlined reconciliation. The dashboard displays receivables, payables, cash flow summaries, profit and loss charts, expenses by category, and account balances at a glance with configurable date ranges. Quotes and estimates convert directly into invoices upon client approval, while recurring invoices and bills automate periodic billing without manual intervention. The modular architecture built on Laravel with the Akaunting Module package enables an App Store where developers publish extensions for payroll, inventory, projects, and CRM functionality. Multi-company support manages separate books from a single installation with per-company user roles. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. BSL licensed.

With 7,400+ GitHub stars, 280+ contributors, and 99 releases spanning 15 years of active development since 2011, Dolibarr is the modular ERP and CRM platform that scales from freelancers tracking invoices to manufacturing companies managing full production workflows — all within a single PHP application requiring only a web server and database. Enable exactly the modules your business needs: CRM with leads, proposals, and online contract signing; invoicing with customer and supplier management, credit notes, and SEPA direct debit; double-entry accounting with bank reconciliation and margin analysis; stock and warehouse management with barcode scanning, batch and lot tracking, and product variants; bill of materials and manufacturing orders with workstation scheduling; HR with employee records, leave management, expense reports, recruitment pipelines, and timesheets; project and task management with shared iCal calendars; and a ticket system with integrated knowledge base for customer support. TakePOS provides a touch-optimized point-of-sale interface for retail shops, bars, and restaurants with floor and table management, QR code self-ordering, automatic stock decrements, and Stripe terminal integration. Payment processors connect via PayPal, Stripe, and Paybox. The marketplace offers over 1,000 third-party add-ons, and the low-code Module Builder enables custom extensions without programming. Deploy via the official Docker image with MariaDB, DEB and RPM packages for Linux, or manual installation on any PHP-capable server. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

Bigcapital gives small and medium businesses a complete double-entry accounting, invoicing, and inventory management platform they can self-host for free, replacing the per-seat subscriptions of QuickBooks, Xero, and Wave. Every transaction records debits and credits across your chart of accounts, automatically generating balance sheets, profit and loss statements, trial balances, general ledger reports, journal entries, accounts receivable and payable summaries, cash flow analysis, inventory valuation, and inventory summary reports. Sales invoicing supports recurring schedules, customer payment tracking, estimate-to-invoice conversion, and configurable GST/VAT tax rates. Purchase invoicing handles vendor bills with expense categorization for payroll, rent, and operational costs. The inventory module tracks stock levels using FIFO and average cost methods, automatically adjusting quantities on every sale or purchase and providing reorder alerts. Multi-currency accounting converts transactions at real-time exchange rates and consolidates them under customer or vendor profiles with detailed currency reports. The platform deploys via Docker Compose with multi-tenant isolation giving each organization its own separate database, requiring as little as 2GB RAM for the complete production stack. A headless REST API with Postman collections lets developers embed the accounting engine into external applications for programmatic transaction management. Role-based permissions control access for team members and invited accountants across organizations. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Quote to cash in one web application - create quotes, convert them to invoices, record payments, track customers: iDURAR is an open-source ERP and CRM platform for small and medium-sized businesses. Built on the MERN stack (MongoDB, Express, React, Node.js) with Ant Design components and Redux state management, it presents a clean SaaS-style interface that needs little onboarding. Core modules cover invoice management with PDF generation and email delivery, payment recording against invoices, quote and proforma handling, customer records, and accounting views over the resulting data. Multi-currency support and localization make it usable for internationally operating teams. Because the whole stack is JavaScript with an API-first backend, extending it - custom fields, new modules, integrations - is approachable for any Node/React developer rather than requiring a specialist ERP skill set. Deployment is straightforward via Docker with a MongoDB instance. Licensed under AGPL-3.0 with free commercial use; a hosted enterprise version exists but the self-hosted edition is fully functional.

With over 37,800 GitHub stars and active development since its first release in 2008, ERPNext is the most-starred open-source ERP system — delivering accounting, inventory management, manufacturing, CRM, project tracking, asset management, HR, and point-of-sale capabilities through a unified web interface built on the Frappe Framework's metadata-driven architecture. The accounting module handles multi-company consolidation, multi-currency transactions, tax templates for GST and VAT, bank reconciliation, and automated journal entries with real-time profit and loss, balance sheet, and cash flow reporting. Manufacturing covers production planning with multi-level bill of materials, work order scheduling, capacity planning, subcontracting, and quality inspection at each production stage. Inventory tracks stock across multiple warehouses with batch and serial number tracing, automatic reorder levels, landed cost calculations, and perpetual inventory valuation using FIFO or moving average methods. The CRM module manages leads, opportunities, and customer communication with email integration, while project management tracks tasks, timesheets, and Gantt-based scheduling with budget controls. Custom applications extend functionality through the Frappe ecosystem without forking the core codebase, and the REST API enables integration with payment gateways, shipping providers, and third-party services. Deployable via Docker Compose or the bench CLI tool with MariaDB and Redis. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

Roughly 40 integrated business apps forming a full ERP: Odoo's open-source suite runs companies end to end. The Community Edition, licensed LGPL-3.0, ships roughly 40 apps covering CRM, sales, invoicing, basic accounting (journals, chart of accounts, taxes, reconciliation), inventory and warehouse management with multi-step routes, manufacturing with BOMs and work orders, purchasing, project management, timesheets, HR, a website builder, and eCommerce. Each app works standalone, but they share one PostgreSQL database and one data model, so a confirmed sale updates stock, triggers procurement, and posts invoices without integration glue. The modular design means you enable only the apps you need and extend with 40,000+ community modules from the Odoo app store covering nearly any vertical requirement. Inventory supports multi-warehouse stock, reordering rules, and lot and serial tracking with barcode-ready operations; manufacturing ties BOMs, work orders, and work-center routing directly to sales demand and stock levels; and the website builder sells straight from your product catalog with payment provider integrations. You can start with just CRM and invoicing on day one and switch on inventory or eCommerce later - new apps integrate with existing data instantly because the schema is shared. The server is Python with an XML/JavaScript view layer, and because data lives in plain PostgreSQL there is no proprietary format: you can query, back up, migrate, and extend business data directly, with unlimited users and no per-seat licensing - where enterprise ERP pricing is per user per month, headcount here costs nothing.

No middleman, no custody, no private keys to hand over: Bitcart is a self-hosted crypto payment processor that settles every payment straight into your own wallet. Connect wallets with just a public key or address; receiving payments never needs a private key. Accept Bitcoin, Litecoin, Bitcoin Cash, Ethereum, Monero, Tron, stablecoin tokens, and Lightning payments, with each store mixing as many wallets as it needs for multi-currency checkout. Issue invoices with custom expiration, promo codes, and per-invoice payment methods, then get status updates through webhooks, Telegram, or email. A ready-made storefront with categories, price filters, discounts, and a cart sells products or digital downloads, while a keypad point-of-sale view with amount, discount, and tip modes covers in-person sales. Approve payouts, issue refunds, export invoices as CSV or JSON, and add extensions from the plugin marketplace in one click. Bring crypto checkout to WooCommerce, Shopify, WHMCS, FOSSBilling, or Odoo, or script your own flow through the REST API. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

BTCPay Server processes Bitcoin payments with zero transaction fees, zero monthly costs, and zero third-party custody of your funds. Payments settle directly from customer to your wallet through a full Bitcoin node that provides cryptographic proof of receipt without trusting any intermediary. Lightning Network integration through LND, Core Lightning, or Eclair enables sub-second confirmation at sub-cent fees, with Ride The Lightning providing web-based node management within BTCPay itself. The Point of Sale app creates storefronts with product catalogs, tipping, and QR code displays for physical retail, events, or web embeds. Hardware wallet support through BTCPay Vault connects Ledger, Trezor, and ColdCard for transaction signing, keeping private keys in cold storage while running a hot payment interface. Multi-tenant architecture allows multiple stores on one instance, each with isolated wallets, Lightning nodes, and user permissions. The Greenfield REST API exposes every function programmatically for headless operation, automated invoicing, and custom integrations. E-commerce connectors for WooCommerce, Shopify, Magento, and PrestaShop plug in alongside Zapier for workflow automation. Optional Tor hidden services expose the instance as an onion address for censorship resistance. The official Docker Compose stack handles Nginx reverse proxy, Let's Encrypt TLS, and optional Tor configuration on a dedicated RepoCloud VPS with guaranteed CPU, RAM, and SSD. MIT licensed.

Behind a storefront you own sits PrestaShop, an open-source e-commerce platform that runs the catalog, the checkout, and the order desk. Products carry size and color combinations, features, brands, suppliers, and categories, CSV import loads products and customers in bulk, and Extra Properties adds custom fields with their own types to products, customers, and orders. The bundled One Page Checkout module, switched on from the back office, puts every checkout step on a guest-first page, and the four-page flow stays available. Hummingbird, the default theme, presents a mobile-optimized, accessibility-minded storefront, and native WebP and AVIF image support helps pages load faster. Staff handle orders, invoices, credit slips, abandoned carts, and returns, create orders by hand, and answer shoppers from the customer service page. Carriers, payment methods, taxes, currencies, languages, and shipping zones are configured in the back office, multistore runs several shops with separate settings, and the Update Assistant guides upgrades through backup, update, and restore. In the Classic edition, an Ask AI assistant answers questions from real store data and runs plain-language requests after asking your approval, using the provider and API key you connect. The Admin API connects ERP, order management, PIM, and marketing automation tools through scoped OAuth clients, and Addons marketplace modules extend the shop. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. OSL-3.0 licensed.

Backed by 23,000+ GitHub stars and trusted by global brands processing millions of orders, Saleor delivers the open-source headless commerce API that replaces monolithic ecommerce platforms with a composable, GraphQL-native architecture where APIs are the only way to interact with the system. The core engine built on Python and Django handles catalog management, order processing, payment orchestration, inventory tracking, and fulfillment workflows while remaining completely decoupled from any frontend technology. Native multichannel support enables per-channel control of pricing, currencies, warehouses, product availability, and payment methods, managing Instagram, Amazon, regional websites, and retail POS from a single backend. The extensibility layer provides 160+ webhooks spanning synchronous payment callbacks, asynchronous event notifications via Google Cloud Pub/Sub and AWS SQS, and subscription queries that shape webhook payloads to deliver only the data your services need. Dashboard UI Extensions offer 45+ mount points for embedding custom interfaces via iframes without forking, while the Apps system allows building payment gateways, PIM integrations, loyalty programs, and discount logic in any language. The React-based administration dashboard provides product management, order processing, customer segmentation, and analytics with multi-language and multi-currency support. OIDC integration connects existing identity providers for single sign-on across the merchant organization. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. BSD 3-Clause licensed.

Built for self-hosted server deployments, Laranode transforms bare Linux installations into multi-tenant web hosting platforms with automated Let's Encrypt certificates and isolated PHP environments without recurring license fees. System administrators can provision isolated user accounts with dedicated document roots, configure custom domains, and deploy SSL certificates across all active websites in seconds. The integrated PHP manager enables per-site runtime isolation from legacy PHP 7.4 through cutting-edge PHP 8.5 releases, preventing version conflicts between separate production web applications. Operators can create MySQL databases, manage database users, inspect active connections, and adjust UFW firewall port access directly from the visual dashboard. An integrated browser-based file manager lets developers browse directories, edit configuration files, extract compressed archives, and modify file permissions without external FTP tools. Real-time telemetry monitors CPU utilization, memory consumption, disk capacity, and network traffic over customizable historical timeframes to catch bottlenecks early. Automated backup routines archive full accounts, individual websites, or specific databases to local storage, remote SFTP servers, or S3-compatible cloud object stores with point-in-time recovery verification. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.