Hi Richard, can you elaborate more on your question? Not sure I fully understand your problem. The jBPM 5.1 installer download Indigo and installs the proper jBPM Eclipse plugin. Maybe you should give the installer a try (see docs for more info).
Hope this helps.
When I try to attach source in Eclipse (Build Path...) I cannot. It says "non-modifiable".
Maybe it's just the release (minor number) of Helios. Because I have another Helios installation (on Windows), probably of diff. major/minor numbers, where I can attach source.
Could you post the difference in versions of the two instances? Also raise a jBPM Jira for the version where it's not working.