does it store our data persistently on your server/system

No — and this is actually one of the real architectural differences from the closed-source competitors like Beefree and Unlayer.

The SDK is fully client-side — it runs in your app, the JSON templates go wherever you decide to store them (your DB, S3, anything). Nothing touches my infrastructure. SDK also has zero telemetry.

The Cloud tier on the roadmap (AI rewrite, real-time collab, MCP, saved modules, media library, comments) is opt-in — you only hit it if you actively sign up.