It’s not hard to make a private server.
All you need is to start the server-executable, open the ports, settup the database and let people register through a webinterface.

You can pull an older version of the server here: https://github.com/LUNIServer/UniverseServer
and a webinterface from that: https://github.com/LUNIServer/UniversePatcher

Also i don’t recommend to use that because as i said it’s an older version and contains less than the public servers.