Valve have released information pertaining to downloadable content (DLC) for their multiplayer zombie masterpiece, Left 4 Dead.

Called the L4D: Survival Pack, the DLC will introduce a new multiplayer mode called, appropriately enough, Survival, and will also include two complete, new campaigns for Versus Mode.

Additionally, Valve will be releasing a Critic’s Choice Edition of Left 4 Dead which will be available at retail this spring (the same time as the DLC), which includes all of the content from the L4D: Survival Pack, as well as the original game, obviously.

Valve will also be releasing a new version of their Source SDK (software development kit) for PC players, allowing would-be mod-makers to finally be able to officially create their own Left 4 Dead campaigns. This SDK will be available at the same time as the DLC, free-of-charge. Regarding Valve’s strategy of supporting their games well after launch, Valve head cheese, Gabe Newell said:

“Since Half-Life launched in 1998, Valve has made continuous efforts to expand the offering of its products beyond what’s included on the day of launch. With Half-Life and Counter-Strike, and more recently Team Fortress 2, we’ve learned that we’re no longer making stand-alone games but creating entertainment services.

“With Left 4 Dead we’re extending that tradition by creating additional gameplay and releasing our internal tools to aspiring developers so they may also create and distribute new Left 4 Dead experiences.”

Right on!