http://www.albisian.freemybb.com/
Looks to me it is here, the user has apparently found out how to edit navtab links, cheers.
Edit:
You cannot integrate an old forum to your adoptables site, especially if it already has lots of members. This is because the uid from adoptables and forum users table wont match. Of course its not a problem if you want no forum integration, but just a link to a forum you own.