IT research firm Gartner is warning open source software makers that Microsoft's pledge to open up its documentation library to third parties carries legal risks for developers who aren't careful about how they access the technical trove.

"Do not use Microsoft's documentation unless you have rigorous processes to keep track of applicable patents," said Gartner, in a new research report.

Microsoft last week announced significant changes to the way it will manufacture and license software -- partly in an effort to appease the EC and other antitrust regulators. Among other things, Microsoft promised to publish more than 30,000 pages of documentation for Windows and client server protocols previously available only through a trade secrets license.

The company also pledged not to sue open source developers that use Microsoft technologies in non-commercial applications.

Gartner said open source developers shouldn't interpret the latter as carte blanche to add Microsoft technologies to their product mix. While Microsoft will now openly publishing interoperability documentation, open source developers who want to use the information still require a patent license from Redmond if the work is for commercial distribution.

Even non-commercial work poses a risk because there's a chance it might eventually turn up in a commercial environment. "Keep all work that depends on these patents separate from other [open source software] work, to avoid exposing downstream developers and users to litigation risk," Gartner said.

The researchers said Microsoft needs to provide more details about how its new, self-proclaimed commitment to openness will affect its patent licensing program. "Microsoft's new interoperability principles go much further than before, but questions remain about Microsoft's royalty terms and conditions," wrote Gartner analysts George Weiss, Matthew Cain, and Nikos Drakos, in the report.

The analysts noted that Microsoft's openness pledge "is not wholly altruistic" as the company is hoping that easier access to its technical documentation will cause some open source developers to jump to the Windows camp. "This will help Microsoft expand the Windows platform as an organic ecosystem," they said.

As part of its announcement last week, Microsoft said it would launch the Open Source Interoperability Initiative -- a forum that will include labs, plug fests, technical content, and "opportunities for ongoing cooperative development" with open source developers.

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.

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."