TaskService constructor tries to load operations-dsl.mvel from current package folder. If called from subclass, the constructor fails to locate the operations file, as package name is different. The suggested workaround forces loading of Operations DSL by traversing the class hierarchy bottom up. If operations file cannot be found, the constructor throws Runtime exception with problem description (instead of NullPointerException). The update allows subclassing of TaskService and overriding Operations DSL. The patch is available through

git://github.com/rushproject/jbpm.git