The US Department of Justice (DoJ) claimed today that competition and consumers have benefited from its antitrust enforcement efforts against Microsoft.

The settlement reached after its long-running investigation has protected the development and distribution of middleware, including web browsers, media players and instant messaging software, the DoJ said.

In a joint filing in the US District Court for the District of Columbia, the DoJ and the states of New York, Louisiana, Maryland, Ohio and Wisconsin submitted a review of the final judgments entered in 2002 to resolve the antitrust case against Microsoft.

"Since the entry of the Final Judgments, there have been a number of developments in the competitive landscape relating to middleware and to PC operating systems generally," the DoJ stated its filing today.

"This suggests that the Final Judgments are accomplishing their stated goal of fostering competitive conditions among middleware products, unimpeded by anticompetitive exclusionary obstacles erected by Microsoft."

The core allegation in the original lawsuit, upheld by the US Court of Appeals in June 2001, was that Microsoft had unlawfully maintained its monopoly in PC-based operating systems by excluding competing software products that posed a nascent threat to the Windows operating system.

Specifically, the Court of Appeals upheld the District Court's conclusion that Microsoft engaged in unlawful exclusionary conduct by using contractual provisions to prohibit computer manufacturers from supporting competing middleware products on Microsoft's operating system,

Microsoft also prohibited consumers and computer manufacturers from removing access to its middleware products in the operating system, and reaching agreements with software developers and third parties to exclude or impede competing middleware products.

"The Final Judgments have been successful in protecting the development and distribution of middleware products and in preventing Microsoft from continuing the type of exclusionary behaviour that led to the original lawsuit," said Thomas O. Barnett, Assistant Attorney General in charge of the DoJ's Antitrust Division.

"The Antitrust Division has made enforcement of the Final Judgments an important priority and will continue to vigorously enforce the antitrust laws in computer software markets."

The Final Judgments are scheduled to expire in November 2007. The DoJ concluded that it was necessary to extend certain provisions relating to protocol licensing until November 2009.

Microsoft agreed to that extension, which was approved by the District Court in 2006.

Microsoft has also agreed that the DoJ and state antitrust enforcement agencies may, at their discretion, apply to the court in late 2009 for an additional extension to all or part of the extended provisions of the Final Judgments for a period of up to three years to November 2012.