The BBC said, in the FAQ on the original Iplayer set up (the P2P version) that it was only available to license holders and that by limiting it to the UK those conditions were, most probably met. The reason for that statement/decree/promulgation or whatever you wish to call it is irrelevant. My logic is, I'm a license holder, I'm entitled to view it location is irrelevant. If they only tell half the story then sorry I'm not clairvoyant.
I must admit I never use it so whether they've changed that FAQ I don't know.