It is pretty trivial to set up something like phpBB (I’m not an IT person, merely an amateur, and I recently set up a forum for CLL patient support), but the big thing is the loss of the existing posts. That is very hard to import. At best one could have the old forum in read only format as well as the new, with links between them.
I think it's fair to say that while we enjoy the forums, they are a sideline for Audiogon, which is a for-profit business for re-selling audio gear.