Thanks a lot Marco
For other readers: I've tried it but it still doesn't work After some examination of the stacktrace:
http://pastebin.com/gu5i2eYE
and my persisntence.xml content:
http://pastebin.com/dJnBwpjK
It may be a classpath problem with dom4j. So I've tried it with removing it from jbpm-console-server.war#WEBINF/lib and from standalone/lib as well as the runtime directory which is created automatically in jbpm-installer on running "ant install.demo". But it still doesn't work.
I would be very happy about geting another nice hint or an already patched version of jbpm using JPA2.