Medievia is one of the largest MUDs on the internet. It was originally based on the Merc MUD engine, which in itself was a derivative of DikuMUD.
People such as Richard Woolcock, known as KaVir on the internet, the author of the GodWars codebase, and Michael Siefert, one of the original Diku authors, claim that it still is. This is a controversial claim as Medievia accepts money from donations, which would be a violation of the Diku and Merc licences.
A large file of leaked Medievia code confirms that at least for some years of its existence Medievia was a DIKU-derived MUD, while it claimed to be completely original.
However, these allegations are a moot point, as DIKU itself was coded on university computers and university time, and are thus in actuality university property.
Medievia's owner Michael Krause claims that these allegations are unfounded as the entire MUD has been rewritten completely in version 4, thus making it no longer a derivative.
Offerring huge, expansive wildernesses, dragon flying, trade runs, dueling, quests, and soon-to-be ships, Medievia will be by far the most in-depth MUD of its time.