I'm using the newest WP and BP on a new install and get nothing when testing this plugin.
I create a group (either in admin at the bottom with the new links or on the front end) and it gives me a choice if a category or a user group. I select category but when I go to make another group I don't have any choices for a category to put it in. On my groups page it says it is a Category Group though.
Any ideas what happened? It appears it does not make any changes to the database structure.