the actor in jBPM is just an ID. It could be everything, a system, role, user, anything. If you can map the user that logs in to a role name and pass that on to jBPM (see the LoginFilter) then you can just use the role as an id.
If you need more functionality, you could use pooled actors. Read the docuementation for this concept.
If you want to customize the tasklist, you have to adapt he home.jsp and HomeBean. Those take care of the tasklist. IS there anything you'd like to have in there?
it is enough for me now.