Hi Keon,
The Identity part of jBPM is most likely to be a demo of real word 'User Manager'. If you want to use jBPM in your project, maybe you should implement a IdentitySession by yourself and put it into the jbpm.cfg.xml. You can find more information in the developers guide.
http://docs.jboss.com/jbpm/v4/devguide/html_single/#customizingtheidentitycomponent