Mr. Newell concedes that this approach has been successful for Apple. He says, however, that he is concerned that Microsoft is taking a similar approach for Windows 8 applications, which will need to be distributed through a Microsoft app store if they take advantage of the most modern features in the operating system. Valve worries that Microsoft’s control will undermine Steam on Windows 8 by creating a bottleneck for updates to games.

“We would say to Microsoft, we understand all these frustrations about the challenges to your business,” he said. “But trying to copy Apple will accelerate, not slow, Microsoft’s decline.”

Mark Martin, a spokesman for Microsoft, declined to comment.

SOME game executives say it’s ironic that such concerns come from Valve, which has become a gatekeeper with Steam. Last year, the company had a dust-up with Electronic Arts over Steam’s policy of taking a cut of all revenue generated from a game, like the sale of virtual goods, even after a player has bought the game. As a result, E.A. is not selling a number of its latest games through Steam.

Valve says that without such a policy, developers could easily game the Steam system by making all their software free and charging consumers for additional content later. It is worth pointing out, too, that E.A. last year began competing directly against Steam by starting its own online game store, Origin.

Valve can do without many formalities of a traditional company because it’s privately held and controlled by Mr. Newell. He and Mike Harrington, who is no longer with the company, founded Valve in 1996 with the wealth they accumulated in Microsoft’s early days. The company has never raised money from outside investors, so it is under no external pressure to sell itself or go public.

Not that Mr. Newell hasn’t had opportunities to sell out. Valve has been pursued over the years by Electronic Arts, which would very likely have valued Valve at well over $1 billion had the talks progressed that far, said two people with knowledge of the discussion who spoke on condition of anonymity because the talks were private.

Although Valve’s finances are private, Michael Pachter, an analyst at Wedbush Securities, estimates that the company could be worth around $2.5 billion today.