You will only be able to play it on PS3 OR PC, valve have an editable license but it won't give you 2 copies of the game to play. As for the pre-order, I traded in a heap of old games to EB, got $180 credit (which is more than I paid for them, proper bargain hunting, ha!) and they guy pre-ordered the Portal 2 Cube Edition for me to price match JB's $79 dollars, so I get a free Rubix's Cube too. Worth looking into if you want to get a Cube, was looking to buy the original Rubix Cube but the portal 2 one will be fun as well.
How exactly would an "editable licence" work? accourding to the escapist you will get a free PC licences. However If you are correct it will be interesting to see how you would register the PS3 version. http://www.escapistmagazine.com/news/view/109246-Valve-Details-Steam-Features-for-Portal-2-on-PS3