Valve Software or Valve Corporation was founded as an L.L.C. based in Kirkland, Washington. After incorporation in 2003, it moved from its original location to Bellevue, Washington, the same city in which their original publisher, Sierra On-Line, Inc., was based.
After the success of Half-Life, the team worked on mods, spin-offs, and sequels, including Half-Life 2. All current Valve games are built on its Source engine, which owes much of its success to mods and sequels. The company has produced six games series: Half-Life, Team Fortress, Portal, Counter-Strike, Left 4 Dead, and Day of Defeat. Valve is noted for its support of its games' modding community: most prominently, Counter-Strike, Team Fortress, and Day of Defeat each began as a third-party mod that Valve purchased and developed into a full game. They also distribute community mods on Steam.
On January 10, 2008, Valve Corporation announced the acquisition of Turtle Rock Studios.
On October 5, 2009, Defense of the Ancients (DotA) developer IceFrog announced that he would be leading a team at Valve to further develop DotA.
Valve announced its Steam content delivery system in 2002. At the time, it looked to be a method of streamlining the patch process common in online computer games. Steam was later revealed as a replacement for much of the framework of WON and Half-Life multiplayer and also as a distribution system for entire games.
Through Steam, Valve has shown substantial support for their games through regular updates. Valve's most recent major update for Team Fortress 2 added four new maps, a new game mode, six additional weapons, 35 new achievements, and additional generic bug fixes. This is the fifth such update in the game's two-year history. A recent update to Valve's newest game, Left 4 Dead, provided seven achievements, sixteen maps (fifteen "remixed" versions of older levels and one entirely new level), a new game mode, and VS support for two previously unsupported campaigns. All such updates are provided free of charge.
As of August 14, 2009, 843 games are available on Steam, and as of February 18, 2009, there are over 20 million user accounts.
Valve Software isn't Garry's Mod developer (wich is Garry Newman), but its distributor through Steam. Garry's Mod use the Source Engine. According to The Steam Review, Valve has given Garry Newman, in exchange for 50% of the profits from Garry's Mod, the full Source engine source code to overcome the limitations of the free Source SDK.