[@zaerl Participant 16 years, 3 months ago]

I have written a plugin called “zaerl Visibility” that can help you hiding forums for guests. Then you can delete the content of the register.php template file, delete the register link on header.php and manually add users with https://bbpress.org/plugins/topic/admin-add-user/ (check the comments for a fix if you’re running 1.0.2)