Multi-User Dungeons, or MUDs, were some of the first multiplayer
       online games. The game called MUD was the invention of Roy Trubshaw
       and Richard Bartle, but a bewildering variety of clones emerged over
       time: AberMUD, DikuMUD, MOOs, MUSHes, and more. In addition to
       gathering documentation on MUD history, the ESS plans to host active
       MUDs.
       
       AberMUD
       -------
       AberMUD was the first open source MUD. A number of versions were
       released over the years, but it was primarily developed by Alan
       Cox, a name which is well known amongst the open source
       community. Among other things he was the maintainer of the 2.2 branch
       of the Linux kernel.
       
 (TXT) AberMUD History(via a forum post by Alan Cox) 
 (DIR) AberMUD Files
       
       Off site links:
       
 (HTM) A Classification of MUDs, by Martin Keegan