Some of you may know, or have even played on, my most recent MUSH, Wing Commander: New Horizon. I shut the game down a few months ago due to inactivity, but as of today you can now download all of the source code and a 'sanitized' version of the game database (missing player information, log contents, etc, but all code, rooms, ships, etc are there).
It's rather an unusual example of a MUSH codebase - there's a complete implementation of a JSON-protocol client/server model that allows external processes to exchange information with PennMUSH. Included is a complete implementation of that protocol in Ruby along with many thousands of lines of Ruby and softcode systems that could be used to build any sci-fi game, or adapted to fit just about any theme.
For more information/downloads, I've set up a page on GitHub.
I'll be around on M*U*S*H for questions/support!