I tried now something new...
I removed the source with PoolingDataSource ds = new PoolingDataSource(); and tried to configure the datasource with Spring. Unfortunaly i have nearly no Spring practice... but we will see ;-)
I included all libs for jBPM by Maven (see this link to get all dependencies) http://grepcode.com/snapshot/repo1.maven.org/maven2/org.jbpm/jbpm-bpmn2/5.1.0.Final
Then some of the libs were not compatible with my current libs... this i could solve too. At the moment i get an IllegalArgumentException when my Entities (not of the jBPM) are instanciated. The problem is: I have really many entities to change and i'm not sure that it will work after this.
If you need just a persistence example without Maven and Spring, i can send you one... i found it in the INET. This works and might help you.