BuddyPress.org

@dennis_h, amen, preach it brother!

Yes, forums are very useful and popular, but they are just another way of displaying a conversation. The basic building blocks for blogs, forums or social networks are the same:

users
posts
comments

If you want a traditional forum view, you could probably create that in your theme.

There is no reason to bolt an external forum script on to Buddypress, with its own database tables etc. It only creates synchronization problems and confusion for the end user.

I have argued this before here and elsewhere.