If Xamarin is open sourced and RoboVM is dropped, I can only speculate that Microsoft did not want to touch JVM with a 10-foot pole and chose to not entertain Oracle legal. May be I am wrong, but that is one possibility.
IIRC, RoboVM is being dropped. No further development work. I could be wrong though, I'm half remembering it being discussed on a Reddit AMA with Miguel de Icaza.
EDIT: It wasn't in the AMA after all, but it has been dropped:
That I'm sure, but the project was only forked 6 months ago, so I'm sure BugVM can catch up, especially given that RoboVM is dead and thus a stationary target at this point.