The latest Eclipse plug-in can now be obtained at:
Indigo: http://download.eclipse.org/bpmn2-modeler/site/
Helios: http://download.eclipse.org/bpmn2-modeler/site-helios/
The "Codehoop" link in the User's Manual no longer works.
However, this version does not fully support jBPM5 (I was told so on a more-or-less official basis). It seems the team developing this has the intention to achieve such support soon.
Hope this helps!
--JE