On a side note: Valve will start its new Greenlight project soon.
Seems like they are still afraid to mention Linux
What systems must my game run on?
To remain in Steam Greenlight and qualify for distribution via Steam, your game must at least run on a Windows PC.
You can be also developing for any other platform you like, but we are only able to support PC & Mac releases at this time.
I'm not sure i understand. They state that project must run on windows, because that's where the vast majority of money is and they are a business trying to make money. Then they state the fact that currently steam works on both windows and macs.
I'm not sure what people wanted.