I think it could differ from MUD to MUD but that wouldn't change the "overall" age of players in the MUD community. I have no demographic info to back this up besides personal experience, but I believe that the personality types of a player can have higher averages of different age groups. So a certain MUD could therefore attract a slightly differing age group than another.

As a side-note, i've also noticed that the average age in the community is in the early 20's, even though I myself started while 13 and now fall into the late 20's category. I also noticed that the gender issue isn't -as- profound as expected, though it is there. Then again, note that this is based on the MUD's I play and is influenced by my personality type. (I play mainly RP) (As a side-note, the second largest group on half of the MUDS I played would be the late 20's/early 30's group)

Actually I think this is an interesting enough topic that it may merit the creation of a web script (similar to the Bartle test, though with some modifications) to grab these demographics.

Kaylus@Solice