online The game called MUD was

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.

AberMUD History(via a forum post by Alan Cox)

AberMUD Files

Off site links:

A Classification of MUDs, by Martin Keegan