Don't quote me, but I think the partnership is meant to address tooling and doesn't affect us implementing a bpel engine.
The partnership is more specifically between the JBoss ESB and Active Endpoints. It is unrelated to jBPM's BPEL subproject which will continue on. If you are interested being a contributor to jBPM's BPEL subproject please raise your hand as there is plenty of things to do! :-)
The JBoss ESB allows for "plug & play" core services such as BPEL, transformation and routing engines and will allow multiple implementations to plug into its architecture. The jPDL version of jBPM is already integrated with the ESB 4.2 but other process engines can be easily linked in as well.