I suggest you take a look at the Designer included in jBPM5. It is based on Oryx but has been enhanced significantly. It also supports BPMN 2.0, the latest specification for business processes, not the proprietary jPDL language anymore. You can use the jbpm-installer to install a working version. The source code can he found here:
https://github.com/tsurdilo/process-designer
Kris