Author here.

celld and workerd give you Durable Objects if you run another daemon. This is a library your app loads, with state stored in the SQL database you already have (Postgres, MySQL and SQLite supported). No daemon required, no new infrastructure and monitoring, no broker, and no vendor account.

Pre-1.0, MIT, TypeScript, in browser (with WASM SQLite), and Ruby too. Happy to answer anything.

Why chose the Solid- line of naming, considering that's the rails provided naming. I makes it look like this is official.