Unfortunately, the article does not go into more detail around Valve's decision to abandon Linux support for Steam. It is evident by the discovered code that Valve has at least experimented with the implementation. Based on the Steam version for Mac, it is safe to assume that porting to Linux would likely not prove to be too difficult (as Mac is built from a Linux core).

What the article did suggest, however, is that Valve was already swamped with managing the various platforms Steam currently delivers to. For example, the launches of Left 4 Dead 1 and 2 were only for PC and Xbox, but the release of Portal 2 added two additional platforms: Mac and Playstation. Although many games from other publishers come out in numerous platforms, Valve seems dedicated to keep their quality of game strong and feels that games get "diluted even further" as additional platforms are supported.

The code that began the speculation of Steam on Linux cannot be ignored, and is indisputable proof that Valve has looked at Linux as a gaming platform. In the mean time, however, we'll have to take comfort in, not that we can actually shoot zombies in Ubuntu, but that we may actually be a litter closer to that virtual reality.