Lemon Squeezy's license API is $29/month. KeyMint does the same as a one-time purchase you self-host. Generate, validate, and revoke license keys for your digital products. Track activations and expiry dates. It ships as full source code (React 19 + Express 5 + Postgres) — drop in a Neon connection string, deploy to Vercel for free. Not a hosted SaaS. You own the code and the database. Live demo, no signup needed.