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.