BuddyPress.org

One thing to consider is that it is supposed to work that way, otherwise all you have is a standard old-fashioned bbPress setup. Groups give forum topics context, which gives user something to rally around topically. If a forum isn’t part of a group, then eventually all your topics will blur and you will be awash in a sea of unrelated postings. (which is the state of most b-board systems today, imho