The bbPress Membership add-on allows you to restrict access to forums, topics and replies in your bbPress forum.
When creating forums, topics and replies in bbPress, you will see the option Membership Access option. There you can select which membership groups can view the content.
When you return to your membership group in Exchange, you will see in the Content Access area, the forums, topics and replies you restricted to that membership.
You can also continue to add restrictions from within the membership group, including forums, topics, replies and also topic tags.