Is it fully self-hostable? A lot of the time you have to hunt down small clauses in tools like these that state that some essential part of it can't be self-hosted.
We open sourced all parts of Instant with this repo. There are no other private repos. The backend is written as a multi-tenant system, but you could run it with a single 'app'. If you try to set it up and have any issues, please let us know.
