I've never heard the term "learning community".  However, Peter Senge and
his colleagues use the term "learning organization" as a central concept in
The Fifth Discipline and (more practically) in the Fifth Discipline
Fieldbook.  In my opinion, the concepts and processes outlined are simply
individual capacity building and community development, "repackaged" for the
corporate world.  Interestingly, a lot of folks involved in cd and hp use
the fieldbook extensively - myself included!!

I also wonder if "learning community" has anything to do with action
research and particapatory planning models?

Hope this helps.  Shelley Adams