Think of ifMUD as a kind of open house potluck sort of thing. The door is open -- feel free to come in, sample the spinach dip, mingle a bit. If you have something to contribute, be it something thoughtful, something funny, or even a really good Inform hack, chances are that you'll be welcomed enthusiastically. If you prefer to just sit in a comfy chair and watch the people go by, that's perfectly fine as well. But if you run around the house knocking over vases and scaring the cat, the odds are good that you will be asked to leave.
Of course, on a lot of MUDs, running around is the whole point; but ifMUD is not like other MUDs you may have visited. Visitors have occasionally asked, "Hold on -- is all you people do sit in this one room and talk for hours?" Answer: absolutely. ifMUD is a chat MUD. It's possible to do other things on the MUD -- wander around, create objects, that sort of thing -- but we generally only do such things when it enhances the discussion in some way. When it disrupts the conversation, such activities are actively discouraged. This would include constantly wandering in and out of a room where people are trying to talk; creating objects and playing with them in a room where people are trying to talk; using the "emote" command to get into shoving matches or tickle fights in a room where people are trying to talk; that sort of thing. There are plenty of MUDs where you can blow each other up in spaceships or smite one another with your +8 vorpal swords. This isn't one of them.
So what do we talk about? The nominal theme of the MUD is interactive fiction; discussion of IF is pretty much always welcome. That said, visitors to ifMUD will find that the conversation is far from limited to IF. Most of the ifMUD regulars have known each other for a number of years now, have hung out with one another in real life, and so forth; we're a group of friends, and talk about all kinds of stuff, just like you might with your group of friends. And like any established group, we have our own sense of humor, our own set of in-jokes, our own standards of what's acceptable to talk about and what isn't. For your first few visits to the MUD, it's usually a very good idea to lurk a bit and discover for yourself what we're like and whether we strike you as the type of folks you'd have fun hanging out with. If so, great! But no MUD can be all things to all people, and we're no exception. We're pretty happy with the community we've developed, and are rather set in our ways by this point. So stay off our lawn, you gol-dang kids!
(A similar 'charter', though one not developed for ifMUD, was written by Magnus Olsson for the rec.[arts|games].int-fiction newsgroups and is available here.)