Kimai is the #1 open-source time-tracking application. From freelancers to companies and organisations - everyone can manage timesheets, generate reports, create invoices and so much more... Web-based multi-user application, available as On-Premise or SaaS version: https://www.kimai.org
Open-source, self-hosted billing for AI products: price tokens by model, sell prepaid credits, see margin per customer, and charge through Stripe without the Stripe Billing fee.
A production-grade, dependency-free Go SDK for the entire [Xero](https://developer.xero.com) API platform — Accounting, Assets, Files, Projects, Bank Feeds, Finance, Practice Manager, App Store, eInvoicing, and Payroll (AU/NZ/UK).
Pure cost-model substrate for the AbsoluteJS PaaS. createPlan + computeInvoice turn @absolutejs/metering usage snapshots into integer-micros invoices — no float drift, no SDK peers.