They've positioned themselves so that none of their IP even matters as far as their core business goes. What does matter is that they own the marketplace for games. Giving the source code away only allows people to improve the platform, which only strengthens their hold on the market place.

Not if somebody modifying it to use with his own marketplace, which is unlikely but possible with the open source software.

> Not if somebody modifying it to use with his own marketplace, which is unlikely but possible with the open source software.

People have been doing that on PCs for ages. So far Valve seems to be doing well with "well, then, we'll just outcompete" as a solution to that issue.

I'm not sure if they're open sourcing the actual code for steam... it sounded like just the OS. None the less, code doesn't make market places. It takes effort, good faith, proper marketing etc.