Re: How to create a forum that isn't associated with a group?
Another idea is to have all non-group-specific forums belong to a sort of invisible, public group that everyone on the site is a member of. That way, anyone could post to the forum, and its topics would show up in the forum directory as you’d expect.
The trick would be to get that group not to appear on group directories, both public and individual, since the group would be nothing more than a shell for public forums and thus wouldn’t have any other content worth listing on people’s group and activity pages. It’d be easy enough to add a piece of metadata to each group that determined whether it should be listed in directories (independently of the public/private/hidden distinction). The problem is that groups are listed in lots of different places in BP, and you’d have to hijack each one of them in order to filter for this metadata. Such a plugin would be a pain to build and to maintain, I expect, as group lists are posted in more and different places throughout BP.