In reply to simo:
"Seems like a lovely license for Castle, essentially they're getting free developers if any work done becomes their IP. I can't see this flying with the FOSS brigade or Castle's commercial customers, so the only developers are going to be existing RO users.".
I think the license idea is good since it ensures pretty much the same as GPL does: Enhancements are fed back for all the enjoy.
Just think about how many gadgets use Linux despite GPL and then have to open up their source. Those gadgets are sometimes even more intersting than closed source ones since some community starts developing enhancements which then feed back to others or even come as an upgrade. And some commercial developer can always run part of the code on their gadget as an application which doesn't need to be open sourced...