Valve has started advertising for gamers to test and provide feedback on its Steam for Linux beta.
Only "experienced Linux users" need apply, which can be done by submitting an application form which is accessible to owners of Steam accounts. Potential testers must run Ubuntu 12.04 or above.
The beta will exist as a very basic form of Steam for Linux and will feature only one Valve game – the multiplayer Left 4 Dead 2. Participants involved in the testing process will also lack access to Steam's Big Picture mode.
The move fulfils Valve's July promise to make Steam for Linux a reality before the turn of the year.
Managing director of Valve (and former Microsoft employee) Gabe Newell cited the launch of Windows 8 as a contributing factor in Steam's Linux shift. But Microsoft's latest OS will be "a catastrophe for everyone in the PC space," since Microsoft will be able to restrict what it sells on the Windows Store, Newell said.
Valve may also be expecting Linux, which is currently the world's third most popular desktop OS, after Windows and Mac OS, to gain a considerable boost from the uncertainty surrounding the introduction of Microsoft's new OS.
However, Valve's plans were met with criticism from software freedom activist Richard Stallman, who maintains that the purpose of free and open-source software is "to bring freedom to the users."
Last month, Valve released Greenlight, a service enabling users to help Valve decide which games should next appear on Steam's download service.