Microsoft, facing new antitrust investigations in Europe, published 30,000 pages of previously secret software code for its ubiquitous Windows operating system on its website, in what the company described as a significant concession toward greater openness and compatibility with competitors.

But the European Commission and some of those competitors reacted coolly to the disclosure by the world’s largest software maker, noting that Microsoft had made similar claims in the past which turned out to be only small changes in the status quo.

“The commission would welcome any move towards genuine interoperability,” the commission said.

“Nonetheless, the commission notes that the announcement follows at least four similar statements by Microsoft in the past on the importance of interoperability.”

Microsoft lost a landmark court case in Europe last autumn and in October abandoned its appeal of the commission’s judgment in 2004 that it had abused the dominance of its Windows operating system to gain unfair market advantages. But the legal surrender, coming at the end of almost a decade of litigation, did not end Microsoft’s problems in Europe.

In January, the commission opened two new investigations into Microsoft's business practices — one related to the interoperability of its Office suite, server and open-document format, and the other into its practice of bundling software applications like its Internet Explorer Web browser into Office.

The chief executive, Steve Ballmer, said the decision to publish documentation for Windows — previously available for a license fee — was a significant change in philosophy and a recognition that consumers are demanding interoperable software.

Ballmer said Microsoft would publish “thousands” more pages of similar documentation on its website starting in April. “These steps represent an important step and significant change in how we share information about our products and technologies,” he said.

Microsoft said it would sell licenses to individuals and companies wishing to sell products developed from its software coding. Brad Smith, Microsoft’s general legal counsel, said the concessions were real and not just meant to sway European regulators.

“This documentation took years and millions of dollars of software engineering work to create,” Smith said.

But critics said Microsoft’s claims were overblown, and noted that businesses wanting to sell a product based on Microsoft software would have to pay substantial license fees.

“The announcement is still all about the rest of the world interoperating with Microsoft on Microsoft's own terms, not the other way around,” said Thomas Vintje, a lawyer representing the European Committee for Interoperable Systems, a Brussels-based group representing Microsoft competitors like Adobe, Nokia and Oracle, which brought one of the new complaints that led to the current EU commission investigations of the company. “The world needs a permanent change in Microsoft’s behavior, not just another announcement,” he said.

The New York Times