@Sankalp: The public puppet server is not officially archived, at least from a GitHub archive sense. It hasn't received updates since Puppet Core was created and released so it is quite far behind in terms of CVEs and fixes and improvements.
If you are looking for what has happened with the Perforce Puppet Core releases since then, you can catch up on the release notes on the docs site!
Puppet release notes | Puppet Core | 8.17.0
As
@bastelfreak mentioned, the OpenVox project remains open source and is forked from the original open source repos. So if you have OpenVox installed, you'll want to look at the source on that project.
However, if you have Puppet Core installed, you can't currently see the source code for the server of that installation.
What are you currently running? And what are you trying to solve right now? That might help the gang here direct you best.