This is the source code that powers ripple, a private/custom osu! server that has been in development for longer than I'd like to admit. (there's actually a longer history and commit log, but that's part of the shitty code).
Apart from the usual stuff you'll find even in the shittiest of custom/private bancho clones, Ripple has spectating, aaaaand *drumroll* multiplayer!
Want to have some fun? We have a discord server where you can smoke some weed with us.