I think that's because it's a different publisher (i.e. farmed out to Aspyr). It...

		JimmehAH on Jan 22, 2013 \| parent \| context \| favorite \| on: Valve starts promoting Steam for Linux to Windows ... I think that's because it's a different publisher (i.e. farmed out to Aspyr). It's also the same version that's up on the Mac App Store which has limited multi player functionality.