For the Python geeks in the crowd, it uses the Twisted networking framework's IRC module, although it does a lot of the actual messages sent by itself (as it needs to specially craft the multiple recipient PRIVMSGs -- such behavior isn't directly supported by Twisted).
No source code until release, but believe me, the world will see some.
Here's a sample of the bot at this point in action. Currently, you can wander from room to room, and talk to people in the room you're currently in. (Parts have deliberately been edited for what I hope to be obvious reasons, also note that I'm currently running with a two-room test world, it presently supports rooms as large as can fit into memory but it has leaks all over the place)
[18:24] <roothorick> login ********
[18:24] <NonseMUD> Please Wait...
[18:24] <NonseMUD> Welcome back, roothorick!
[18:24] <NonseMUD> You are standing on a small outcropping, with 500-foot drops all around you, except to the south, where instead rests what appears to be a featureless white cube with a 6-foot-by-6-foot hole in it. It's a sunny day.
[18:24] <NonseMUD> Exits: s
[18:24] <roothorick> work you *****
[18:26] <roothorick> cool
[18:26] <roothorick> can you see this?
[18:26] <NonseMUD> <disturbed> yea
[18:26] <NonseMUD> <disturbed>
[18:26] <NonseMUD> <disturbed> sup
[18:26] <roothorick> it seems to be working
[18:26] <NonseMUD> <disturbed> this is elite
[18:26] <NonseMUD> <disturbed> dude i love this ting
[18:26] <roothorick> lol
[18:26] <roothorick> it's nowhere near done
[18:27] <NonseMUD> <mati> hello morons
[18:27] <roothorick> mati!