Actually GQ confirmed (and by the way it was GQ out of the UK who did the photo shoot) that Donald Trump INCORRECTLY blamed Ted Cruz as being the source of the attack. They did not comment on how the picture was obtained, however, given the amount of such photos on the web my guess is it has lost its copyright protection.
http://www.gq-magazine.co.uk/article/donald-trump-melania-trump-gq-photo-shoot
There is nothing at the link relating to WHO BOUGHT THE RIGHTS to the photo in question.
I doubt anyone did. I imagine that the photo was simply appropriated 1AM blogger-style. Then in similar 1AM blogger fashion a 15 minute photoshop job was done on it adding a couple lines of text and it was posted on Facebook. This is pretty minimalist stuff.
I don’t see anything here that rises above the level of everyday amateur pranking.