The company said it is adopting four new "interoperability principles" to guide its revised business practices.
First, Microsoft will work to ensure its products feature "open connections" that will allow outside developers to more easily write programs that interact with its own. To that end, Microsoft will publish on its Web site more than 30,000 pages of documentation for Windows client and server protocols previously available only through a trade secrets license.
For patented protocols, Microsoft said it would offer licenses on "reasonable and non-discriminatory terms." Open source developers can access the protocols for free for noncommercial use without fear of lawsuits, Microsoft said.
Secondly, Microsoft pledged to support new data portability methods that will allow information stored in Microsoft products such as Office 2007 to be accessed by other programs.
Microsoft also said it would more fully embrace industry standards in "high volume" products such as the Windows operating system to enhance interoperability with third-party software.
Finally, the company said it would increase communications with customers, IT managers, and the open source community "to drive a collaborative approach to addressing interoperability challenges." For instance, Microsoft is launching the Open Source Interoperability Initiative -- a forum that will include labs, plug fests, technical content, and "opportunities for ongoing cooperative development."
Microsoft CEO Steve Ballmer in a statement called the policy revisions "an important step and significant change in how we share information about our products and technologies."
Other Microsoft officials said the shift reflects the company's recognition that the software market is becoming an open ecosystem in which products not built to standards and lacking interoperable features will wither.
"This will become even more important in the coming years as loosely coupled systems become a basic requirement for business success," said Bob Muglia, senior VP for Microsoft's server and tools division.
Technological motivations aside, Microsoft has come under significant legal pressure to make its products more open to third-party developers.
Europe's competition watchdog last month launched two new antitrust investigations into the company's business practices.
The European Commission is eyeing the possibility that Microsoft is violating monopoly laws by failing to make its products interoperable with competitors' offerings and by illegally bundling its Internet Explorer Web browser with Windows.
The EC launched the investigations following a complaint from Microsoft rivals that have banded together in a group called the European Committee for Interoperable Systems. ECIS comprises Sun Microsystems, Adobe, IBM, Oracle, Red Hat, and several other vendors that compete with Microsoft.
The probes mirror earlier EC actions against Microsoft that resulted in $1 billion in antitrust fines. The penalties were upheld in September by Europe's second highest court.
Muglia on Thursday acknowledged that the company's policy changes were in no small part motivated by the court's decision. "It's an important step forward in our ongoing efforts to fulfill the responsibilities and obligations outlined in the ruling of the European Court of First Instance in September 2007," Muglia said.
Microsoft's commitment to greater cooperation with competitors could also ease antitrust concerns that might arise if the company is able to successfully negotiate a buyout of Yahoo.
Microsoft has offered about $41 billion for its rival. Yahoo to date has rejected the proposal.