Um, yes, it's possible. SteamOS is an open-source Debian fork. The only thing proprietary in the whole package is the Steam client itself, which you aren't at all required to leave installed.

Not to mention the improvement to drivers, etc, will rise the tide for everyone.

You could install wine on it and use it to run photoshop if you wanted whie mining bitcoins and running an apache webserver. It is a linux box on pc hardware. Never mind install, you could develop another store on it.