I do not have the forums tab showing during group creation on a new site that I am building. Forums are created when the group is formed though and the tab is there within the group.
The forums tab is also present during forum edit.
Not having it at creation means that creators can't set permissions.
I did not originally publish the 'CB GroupJive Forums' plugin but have done now.
GJ 2.7.0
CB 1.9
Joomla 2.5.9
Kunena 2.0.4 plugin Kunena - Community Builder Integration enabled