it was a hard decision
YAWL is not BPEL compatible.
YAWL is not WFMC compliant
YAWL is still under development, some how more complete than some workflow  engines but not as complete as some others specially the quality of code is still poor.

I think BPEL will be feature standard if bpel4people is implemented good.
WFMC is a bad standard in my opinion.

YAWL is theoretically correct.
YAWL is based on workflow patterns concept.
after studying JBPM, some WFCM compliant engines and some BPEL engines we decided to go over YAWL, because it was more theorically correct and more expanable than other engines.

I think jBPM is good for java developers to use inside a java system but not good for system which end users want to interact with workflow.