So, this is because it's an older game? Or are the going to be getting into the virtual goods business?
I imagine Portal downloads and purchases have also probably reached all-time lows. With the press coverage and meme-ification it got, there are probably very very few people left who would be willing to buy it, and have not because they haven't heard of it yet. Thus, by giving it away free to people who wouldn't have bought it anyway, no money lost.
Secondly I would think they've decided most people that are going to buy it, have already. So why not try to pick up more fans before the second one comes out this fall.
old: 1 having lived for a long time; no longer young
portal is no longer young, older seems reasonable to me.