That's an authorization issue, sure, but Netflix doesn't charge you any extra for it.
I wish it weren't the case, but what they've stated in the past is you will have to purchase and enter PS3 registration codes to be able to do it. Down the road that can probably be had for pretty cheap, but to do it at launch will be the full purchase of another copy of the game. And presumably future expansions, too.
Before anyone slams me, I do NOT think this is a good idea idea and I wish it were different. I can hope they'll reconsider their stance on the issue but I'm not going to hold my breath.