In continuing with its theme of strategic benevolence, Valve will today release the anticipated isometric action shooter, Alien Swarm, through the company’s Steam digital distribution service for the grand total of nothing.

That’s right: Today, from Steam, you’ll be able to download what looks to be an authentically excellent action romp absolutely for free.

Oh, that’s not enough for you? Well, what if Valve throws in the complete code base and SDK (Software Development Kit) for Alien Swarm as well, so would-be videogame programmers and creators can learn how the developers of Alien Swarm went about making the title.

Surely you’d be willing to pay ‘Free’ for that package!

Alien Swarm began life as a modification for Unreal Tournament 2004, and was released in 2004 with patch and update support following its launch. In 2005, the team behind the Alien Swarm mod, Black Cat Games, began work on a commercial version of the game based on Valve’s Source engine that, until recently, was thought to have been cancelled.

It turns out, however, that instead of being cancelled the team at Black Cat Games was hired by Valve. In the interim, those team members have been contributing to the development of Left 4 Dead and Portal 2, but over the years, they’ve managed to continue development of the Source version of Alien Swarm.

Now, the results of their efforts will be released for free, today, via Steam, along with the source code and SDK used to create Alien Swarm. In addition, updates made to the Source engine during the creation of Alien Swarm will be made available to other developers, too.

Alien Swarm “thrusts players into an epic bug hunt featuring a unique blend of co-op play and squad-level tactics. With your friends, form a squad of four distinct IAF Marine classes. Plan your attack using an unlockable arsenal of weapons with countless loadout configurations against a wide variety of aliens.

“Blaze your way through an overrun, off-world colony, eradicating the alien infestation in environments ranging from the icy planet’s surface, to a subterranean lava-flooded mining facility.”

Here’s a nice bullet point list of features for Alien Swarm:

• Tactical, 4 player co-op action game with a top-down perspective
• Complete game code and mod tools
• Unlock persistent items by gaining levels
• Over 40 weapons and equipment with countless loadout configurations
• 4 unique classes and 8 unique characters
• Matchmaking, Steam Cloud, Steam Stats
• 64 achievements
• Tile-based map generation tool

Visit the Alien Swarm official website to drop in on the forum, and be sure to head on over to the game’s Steam page, where you’ll be able to download the game just a little later today (you’ll need the Steam application and a Steam account).

Catch the latest trailer for Alien Swarm just a little ways below:

Alien Swarm – Trailer