No offense, needs some work:
Green doesn't fit it.
The fade effect for the individual forum stats isn't appealing.
Sign In button is jacked up.
Search button is hidden by forums/hook.
And it overall seems a bit plain.
But that is just my opinion.
Good job, better than what I could have done.
I am no coder, but I would say that is near impossible to do without having two copies of forums running at once or at best two accounts being created at once...either way it might be a mess...
Perhaps there is a module that can be made, if you contact IPS for freelancers or you ask a modding website for IPB, however, and again I am not a coder, the only solution I see to this would be to have another website (perhaps a blog website) that runs independently of the two, and have it feed off of the account systems from the other two.
Theoretically, salavador21 is correct. If the forum is moderated, and the moderators had ample time (ESPECIALLY with a warning), then they can become liable. Again, I doubt there are many suits for anything like forums, and if they are, intellectual and technical property generally is dismissed.