Play Amnesia, get Portal 2 released sooner!

[Tottel]

Huh? What is wrong with his English? It's much better than yours, Fomzo the troll.

Secondly, Justine is currently a steam-exclusive expansion to the game. As Mothhive said, you can help Portal 2 be released sooner.
After the release of Portal 2, it will server no more purpose to be exclusive to steam (well, nearly none), and all the non-steam buyers will get access to it as well.

And to my understanding, you are a non-steam buyer.