With neon being bought by databricks, serverless Postgres tech has effectively disappeared from the market.

What do you mean by this? Neon is still operating the same service.

Source: I work there.

Oh my bad! I was under the (evidently mistaken) impression that since they were bought by databricks they would just become a part of that and cease to be.

Evidently, I was very wrong, which I’m glad to hear tbh.

is it open source? (this? https://github.com/neondatabase/neon.git ) and since it's serverless, in terms of being on the internet what are you saying has disappeared, a proprietary version? support/consulting contracts?

There is also this one from Supabase: https://www.orioledb.com/