Server Family: DikuMud
DIKU mud, is a MUD, or Multi User Domain. Created in 1990 and 1991 by Sebastian Hammer, Tom Madsen, Katja Nyboe, Michael Seifert, and Hans Henrik Staerfeldt at DIKU, (Datalogisk Institut Københavns Universitet), the department of computer science at the University of Copenhagen in Copenhagen, Denmark.
Taking its name directly from the department, and known as just DIKU in general, this MUD codebase formed - and continues to form - the backbone of the MUDding community, with almost every mud codebase since, based off of it, after the source code was released free for non-profit use in 1991.
The Diku Family Tree
DikuMUD and its derivatives sprawl so far and wide now, that they make up two thirds of all MUDs currently on the market.
The Diku license does not permit unrestricted use. In an early parody of the GPL license, the Diku license includes the following requirement: "You may under no circumstances make profit on *ANY* part of Diku in any possible way. You may under no circumstances charge money for distributing any part of Diku - this includes the usual $5 charge for 'sending the disk' or 'just for the disk' etc."
This has filtered down to all derivative codebases, such that anyone considering a commercial MUD, or any other textual, interactive platform, cannot consider any of the above codebases, as all are influenced by the original Diku license.
Diku was not he first MUD, that honour lays with 'British Legends' in 1979. However, it was one of the first to become truly popular, and addictive. Diku was the first serious attempt to bring Dungeons and Dragons to the multiplayer online environment, and as such, it secured a strong following.
The mechanics for Diku proved so good that EverQuest adopted them, as the basis for that massively multiplayer RPG.
The last official release of Diku was Diku Alfa in July 1991.