The situation with jbpm-3.2.3.GA and below is that there is no stable public API defined for it. As a result, application code depends on implementation detail that might change without prior notice between the versions.
To fix this we are going to define a BPM API which is going to bee the standard of how you work with BPM in JBoss.
For more on this, please go to http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4160822#4160822
There is some preliminary things to see. Please check http://www.jboss.com/index.html?module=bb&op=viewtopic&t=145775