Several components are open source as their own projects (see below) which will allow you to reproduce most of the features on top of regular Postgres. But the storage part is not open source. We are considering a simpler implementation of it that would be realistic to self-host and still do copy-on-write branching.
These are the open source components:
* pgstream for the anonymization from the production branch
I think when people look at Neon, the Aurora-style disaggregated compute/data architecture allowing highly scalable read replicas on cloud storage is the defining feature, and it's the only such project that offers it for Postgres. So the storage part is the point.
These are the open source components:
* pgstream for the anonymization from the production branch
* pgroll for schema changes
* Xata Agent for the LLM-powered optimizations