Valve will release the Left 4 Dead 2 beta build to a wider audience next week, allowing anyone who already owns the title to play the version of the game where the developer performs testing. In addition to gaining access to the Extended Mutation System in the Left 4 Dead 2 beta build, users can also test the Linux version of the game.
The Left 4 Dead 2 beta build — a separate download from the main game — will begin appearing next week in the Steam library of those who own the commercially released version. It only connects to other players participating in the beta and to beta servers, Valve notes, and players who are bandwidth constrained "might want to wait for the changes to move to the main game."
Left 4 Dead 2 was one of the first Valve games announced for Linux support, but a release date for the game has not been announced.
Valve announced L4D2's Extended Mutation System in February, releasing it to beta testers. The game's EMS is designed to let modders create deeper, more customizable maps and Mutations.