It's a nonviolent MUD. (Multi-User Dungeon)
You can launch the server either via SLIME by evaling mire.el from within Emacs (preferred since it gives you access to the REPL) or by running the included mire.sh shell script.
Dependencies (clojure, clojure-contrib) are included, though you will need a JVM on your system.
To connect as a player, simply telnet to port 3333, or hit M-x mire from within Emacs if you have used mire.el.
This code is not that interesting as a game, though I suppose something fun could be built using it as a base. The primary purpose of it is as a demonstration of how to build a simple multithreaded app in Clojure.
Mire is built up step-by-step, where each step introduces one or two small yet key Clojure principles and builds on the last step. The steps each exist in separate git branches. To get the most out of reading Mire, you should start reading in the branch called step-01-echo-server and continue from there.
While you can learn from Mire on its own, it has been written specifically for the PeepCode screencast on Clojure, which should be released early March 2009.
Copyright (c) 2009 Phil Hagelberg Licensed under the same terms as Clojure.