Sony can't do anything. Some USERS compiled it and put it up somewhere, they can't take on OpenPandora for that. Not even a close call. And it's not in the official apps store anyway.
Also, there is already a version available for maemo, dingoo and what more. Can't possible take them all on and indeed pandora would be too small a fish.
IMO, nothing to worry about. (No law expert though)
Cheers!