It's going to be real GNU/Linux. Anything that will work on it will work on normal desktop GNU/Linux and vice versa. It just might be a bit more locked down to prevent retards from running stupid commands or something.
The point is; It will cause a ton of support for making linux games.
Every one of you should be happy about that. This benefits you and Valve. What Valve wants out of it is:
1) Get away from windows, which is completely subjugated to MS control, for linux which is free and open source, on top have having vast technical/practical benefits.
2) Enter the console market.
They are killing two birds with one stone, and helping linux at the same time.
By the way, I went to gamefaqs, gamespot, and IGN forums to discuss it today. Some retarded shit has been said about it, basically people who have no clue even remotely what "operating system" means and just thinks everything is "windows".