no, but dokuwiki is a snap. ubbdev has an excellent writeup by Myke on how to do it. he wrote it so even {cue geico commercial}a caveman can do it {/end}
i looked @ the mediawiki auth stuff and it doesn't look too bad. one thing to note though, it's not as flexible as either dokuwik or pmwiki..
i know that mediawiki is the king of wikis, but for a forum i'm not so sure you'd need it... unless there is an already in place dealio or it's somehow flat spec'd.