Hyperswitch from Juspay delivers the most comprehensive open-source payment orchestration stack available — a Rust-built platform that connects to Stripe, Adyen, Braintree, Worldpay, Checkout.com, Cybersource, and 120+ payment processors through a single API integration. Intelligent routing drives each transaction to the processor with the highest predicted authorization rate using rule-based, volume-based, and machine learning algorithms, while seamless failover and automatic retries recover revenue from declined transactions using 30+ parameters including decline codes, card BIN, transaction size, and region. The PCI-compliant card vault stores payment methods securely in a dedicated service separate from the main application server, and the reconciliation engine automates 2-way and 3-way matching with backdated support, staggered scheduling, and customizable audit-ready outputs. The Control Center dashboard provides visual workflow builders for routing rules, payment analytics, and operations management. Cost observability tools drill into scheme, interchange, and acquirer fees to detect anomalies and optimize processing costs. The modular architecture allows deploying individual components — routing, retries, vaulting, observability, or the full suite — without vendor lock-in. The web client SDK collects payment information with prebuilt UI components and supports WooCommerce integration. Deploy via Docker Compose with the app server, control center, card vault, and 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.

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.

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.

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.

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.

AI and API products live or die by usage, and OpenMeter is the open-source stack that measures it, rations it, and bills for it. Your application emits CloudEvents for every billable action; OpenMeter validates and deduplicates them, then aggregates usage in real time so dashboards and enforcement checks never wait for a nightly batch. Meters slice that usage by customer, time window, or any dimension you attach, which turns raw events into answers like tokens per workspace this month. Entitlements decide who gets what: metered allowances with balances and overage, boolean switches for features like SSO, and static JSON configuration for per-customer model access. Grants top allowances up once or on a schedule, resets roll balances over each usage period, and one API call tells your app whether a customer still has access right now. On the money side, plans carry flat, per-unit, tiered, package, or dynamic prices; subscriptions, credit balances, and the invoice lifecycle run alongside, with webhooks announcing everything to your other systems. 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.

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.

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.

Sell from your own server with a store that arrives as a single file: myCart pairs a public storefront and an admin panel with checkout, and there is no plugin ecosystem to assemble first. You manage products with variants that track their own inventory, pricing, and SKUs, and you can sell physical goods, downloadable files, and license keys from the same catalog. Checkout accepts Stripe and PayPal for cards and wallets, SpectroCoin and Coinbase Commerce for cryptocurrency, and a built-in dummy provider that processes free products with no payment setup at all. Buyers can check out as guests or register for a customer cabinet that keeps their orders, re-downloadable files, and issued license keys in one place. The storefront ships in eight languages, English, Chinese, Korean, French, Spanish, German, Italian, and Belarusian, with the language switcher available in both the shop and the admin panel. You upload your own logo, favicon, and tagline from the admin panel and the storefront adopts them immediately with no rebuild. The whole shop runs on an embedded SQLite database with nothing else to operate, or on PostgreSQL when you need concurrent writers and managed backups. Built-in HTTPS support and hardened, separately keyed sessions protect the panel and the customer cabinet. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Why rent your own shop from a platform that takes a cut and sets the rules? Openfront runs the whole store, storefront and back office together, on a server you own. Customers get a fast, mobile-responsive store where they can browse the catalog, open product pages with variants, fill a cart, check out, create an account, and follow their orders. You get the dashboard behind it: products and variants, orders and fulfillment, customers, payments through Stripe and PayPal, shipping integrations, and the everyday work of running a store without ten browser tabs. Stock is tracked across multiple locations with movements and backorders, so a warehouse and a shop floor stop disagreeing about what exists. Gift cards run their full life from creation to redemption, returns and refunds follow a proper claims workflow instead of an email thread, and discounts can be simple codes or automated campaigns. Selling abroad is built in, with multiple currencies and regional pricing, while analytics and reporting show what is actually selling. When clicking through menus is slower than saying it, the built-in AI assistant can add products, change prices, and configure regions from a chat, working inside your own logged-in permissions so it can only do what your role allows. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

One install, many shops: Sylius runs separate storefronts with their own languages, currencies, and countries from a single admin panel. Products are simple or configurable. Define a size option, generate variants from S through XXL, and track stock per variant. Attributes, translations, and a nested taxon tree keep the catalog organized. Prices are set per channel. Catalog promotions add sale badges and struck-through prices. Cart promotions pair rules, like a minimum item total, with actions, like a fixed order discount, optionally behind coupon codes. Shipping methods carry delivery windows, zone eligibility, and shipping and tax categories. Order pages show items, shipping, taxes, promotions, payment state, and customer details. The dashboard charts sales and paid orders over time and lists pending work. A ready-made storefront covers product pages, a cart, checkout with address, shipping, payment, and review steps, customer accounts with order history, and product reviews. Custom frontends talk to separate shop and admin REST APIs, documented in OpenAPI. Every enabled locale adds a translation section to products, taxons, shipping methods, and promotions. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

With over 35,000 GitHub stars and 460 contributors, Medusa is the headless commerce framework that gives development teams full ownership of their e-commerce backend without license fees, per-transaction charges, or revenue sharing. The modular architecture ships over 18 domain modules covering products, collections, categories, inventory, pricing, carts, orders, payments, fulfillment, promotions, customers, users, API keys, and stock locations, each independently usable and replaceable. REST and GraphQL APIs expose every commerce operation to any frontend framework — official starters exist for Next.js with community options for Nuxt, Remix, and Gatsby. The React-based admin dashboard provides out-of-the-box order management, product maintenance, promotions configuration, B2B accounts, and multi-warehouse inventory, extensible via the Admin SDK for custom views and workflows. The workflow engine orchestrates long-running commerce processes like checkout, fulfillment, and returns with compensating transactions for reliability. Over 200 official and community plugins integrate Stripe, PayPal, Klarna, Algolia, Meilisearch, SendGrid, Mailchimp, Contentful, Sanity, and Klaviyo. Native multi-region and multi-currency support handles tax-inclusive pricing, region-specific payment and fulfillment providers, and localized storefronts from a single backend. Enterprises including Viessmann, Makro PRO, and INSPIRED Pet Nutrition run Medusa in production. Self-hosting deploys via Docker or directly on Node.js with PostgreSQL and Redis. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Hosting companies that sell VPS plans, game servers, or dedicated machines get a branded storefront, recurring billing, and a ticket desk from Paymenter, running on their own server. A customer browses a category, picks a free, one-time, or recurring plan billed every few days, weeks, months, or years, and shapes the order with select, radio, checkbox, text, number, or textarea options, some of which carry their own price. Prices can differ per currency, and a setup fee is optional. Payment runs through Stripe, PayPal, or Mollie, with tax rates and coupons set from the admin panel. Once it clears, a server extension for Pterodactyl, Virtualizor, VirtFusion, Convoy, cPanel, Plesk, DirectAdmin, or Enhance creates the service. A daily job issues renewal invoices, suspends overdue accounts, and terminates long-overdue ones. The customer portal covers services, invoices, and tickets in 24 languages, and tickets accept replies by IMAP email piping. Staff work with roles, audit logs, email logs, and notification templates, while API keys and OAuth clients connect outside tools. Optional extensions add an affiliate program, announcements, and Discord alerts. Moving over from WHMCS takes one built-in command that imports clients, products, services, tickets, and invoices from a copy of your database. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Software makers who would rather not rent a licensing backend use Keygate to issue, sell, and enforce license keys from infrastructure they control. You create desktop, SaaS, or hybrid products and sell them as subscriptions, perpetual licenses, perpetual licenses with a maintenance period, trials, or floating concurrent licenses that are checked out, heartbeated, and returned automatically. The admin dashboard manages products, plans, customers, licenses, API keys, webhooks, analytics, audit logs, team members, email templates, and branding, with search, filters, and CSV or JSON export. Your application activates and verifies keys through the license API, enforces per-device or per-user activation limits with grace periods, and can verify Ed25519 signed tokens offline with a public key. Usage metering tracks API calls, storage, bandwidth, or custom metrics against quotas with hourly, daily, monthly, or yearly reset cycles and webhook threshold warnings. Connecting Stripe makes checkout create licenses automatically, follows plan and seat changes with proration, handles refunds and cancellations, sends dunning emails after failed payments, and gives customers a billing portal and self-service license management. Team seats, feature entitlements, purchasable add-ons, scoped API keys, and optional S3-backed release hosting round out the selling stack in one binary with one PostgreSQL database. 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.