Check it out here http://bigonions.net/wp-forums/ it works well with http://bigonions.net/ my MU blog but it is in no way dynamic and is simply a copy of my main theme.
I will, however, release it once it is finished and will provide some kind of tutorial on how i did it as it seems people here are interested.
It is of course not finished at all as i am still editing most of it but you can see the header etc is working ok.
Thanks
Matt