I think you can manually configure the wildfly and add the modules to it at that point you don't have to worry about it and you can remove that target not to invoke in build.xml.
you might go to the maven repository where IBM driver is published or go to DB2 Driver is posted downloadLink
and configure the JDBC driver provided over here JDBC Configurations Details
If you ask me steps .
1. Download the IBM DB2 driver .
2. Go to the wild fly home and create a folder in modules com/ibm/db2/main/module.xml. configure the driver jars ( Look at the MYSQL Example )
3. Copy the driver jar
4. make sure that standalone-full.xml has the JDBC JNDI configuration details before you start the wildfly. (You Seem to have done correctly )
All ready to do go , if you read the build.xml you can modify the way you want.
Hope this helps.
(please do mark answer helpful if you think so )
Moved this thread to jBPM forum, since the question looks very much specific to that project. Someone there might be able to help more.
Thanks for your help, I will try it again.