[KaVir]

Sure, but as different types of mud can immitate each other it's very difficult to categorise them purely by feature. I therefore think it might be helpful to start out the FAQ with a clear definition that can't really be disputed - if you state something like "MUSH refers to a group of codebases derived from TinyMUD", then afterwards you can describe the variants of MUSH (TinyMUSH, PernMUSH, PennMUSH) elaborate on what sort of features they typically offer (compared both to other members of the TinyMUD family and to other types of mud entirely), and discuss the sort of audiences they're usually aimed at.

From what I recall, it's the same with MOO (and although I'm speculating here, by extension I would presume the same is true of POO, CoolMUD and possibly even ColdMUD). There's no technical reason why an LPMud couldn't be set up the same way either, and although I'm not aware of any that are, I don't think it would be a good idea to base the definition of MUSH on the default status of a single flag.

Well the same is true of almost all muds (usually only a small number of dedicated admin work on the server code). In the LPMud family (which was also inspired by TinyMUD), the server is separate from the mudlib, and it's perfectly possible to radically customise your game without ever touching the server code.

Many of the more modern DikuMUDs also have their own scripting languages, which provide enough functionality to perform a fair amount of content customisation.

Some of the more modern codebases also offer embedded languages (for example NakedMUD), while others are written entirely in interpreted languages and can be modified on the fly.