Why are you trying to run Robot Framework directly from Java in your
Maven plugin? Couldn't you simply run it through the system and then
be able to use both Python and Jython interpreters? I think that was
the idea in the prototype version that was created some time ago [1].
Anyway, this discussion is probably better continued on
robotframework-users mailing list.

Lets say a memory issue. Having the Hudson VM starting the Maven VM starting the Jython VM makes just too many VMs for our testing box. It works of course, but take more time than a direct call. all these VMs have a minimum memory consumption of 1GB per VM. And if I would have the option to call it internally, I would do it.

BTW I have processed this further and I solved the issue for random.py - it was just not aware of the /Lib folder in the jython jar, so I added it to the classpath. But then later it failed for something in ntpaths.py or so and I gave up for now, had to be a bit productive.