I extended the CoreModule (and UserEJBLocal) with my own user methods, so they acces my user objects instead of the UserEJB. This works fine for most modules but not for the BB modules because the coupling with UserEJB is very strict (EJB CMR).
I had to change the topicEJB and PostEJB in order to make it work. I only store the User ID and retrieve the UserEJBLocal via the Api object. Maybe this is something you can put in the main line?
Or is there another way of integrating Users from another application?