RebornRec is a locally hosted server for older versions of Rec Room ranging from 2016 to 2020, containing many extra features alongside being able to emulate Rec Room's old servers.
As of right now, RebornRec is not open-source, the files you see in the repo are files the server will download and use as it's running.
More info on getting the server running and certain features will be found on the Wiki.
This project is not affiliated with Rec Room in any way, nor intends to infringe on their copyrights. Distributing old versions of Rec Room is copyright infringement, so that's why RebornRec does not come bundled with Rec Room at all.