Litestream author here. Yes, I could release the replication in Litestream with caveats but it’s mostly a matter of focus. I don’t think I’d feel right trying to support two implementations of replication when only one is recommended.
The new replication tooling will not be fly.io specific. It’ll be Apache 2 licensed just like Litestream. You can run it on any VM-like server. We are also working on making it work on pure serverless platforms like Vercel & Deno in the future.