Go to:
http://www.playpc.pl/ro and fill the spaces ( First 2 spaces are for your first and last name, third space is for your email)
Go to you email you should now have the key, use the steps in this video to activate the key :
http://www.youtube.com/watch?v=gPMmBHZQQCc (Instead of choosing Russia, choose Poland)
Ps: I'm not sure if you need a proxy to get the key from their website, but you do need the VPN to activate the key on steam. And also, I'm not 100% if this is legal, I honestly believe it is, but I'm not sure.
Found this on another forum.
Basicly your getting yourself a polish CD key but steam doesn't want you to use it unless your in poland.
So you use a VPN to make it think your in poland. (the video tells you to do russia, but thats wrong because your using a polish locked key)
Shouldn't get in trouble as the game is the same and your not breaching any release dates/censored versions.
But If you get in trouble for doing such then don't blame me though.
If your actually in poland ignore everything else other than getting the key lol.