This would rather be a question for the users' forum. So next time please post there. jBPM does not support XPDL but uses its own executable format called jPDL. If you are looking for a process engine supporting XPDL there is Bonita. I don't know about a tool supporting a conversation like the one you asked for. But since they are both XML formats you could use XSLT to do the job. So you would be "just" in need to write a stylesheet but you would not need to program directly. However, I don't know how if it makes sense to translate from XPDL to jPDL and if it is really possible for practical use. I somehow doubt it.

Searching a little with google would have given you Sebastian's (correct) answer as well.