Okay well your integration seems just fine with no issues that I see. I registered a forum account and posted a dummy product in reviewpost just fine
http://www.naturalbeautycafe.net/rev....php?product=1
Guests have the ability to view your forum just fine it seems. If you do not want guests to view your reviewpost categories then in Admin => Edit Categories for your category permissions uncheck viewing permissions for the groups you do not want to access reviewpost content. Make sure to check the box apply to children to copy to your children cats of reviewpost as well.