Rmud leverages eventmachine to create a event-driven and concurrent mud server written in ruby.
It's not optimal, or even correctly written right now. Hopefully it will stabilize in the future as my understanding of the concepts increase.
The basics of the engine (connection handling, eventmachine setup and a basic chat server) was done before the Ludum Dare compo, but the rest was done between Aug 25 and Aug 26.