After decades of tenaciously guarding its protocols and APIs, Microsoft Thursday cut some major chains protecting the intellectual property of its Windows and other core enterprise products.

Top company officials, including CEO Steve Ballmer, pledged to make Microsoft's software more open in an effort to foster greater data portability and allow for better interoperability with open source developments.

The announcement, however, was met with skepticism from the European Union, which said in a statement that Microsoft has made four similar statements in the past. (Read who we think are the winners and losers from this move.)

The reversal, in part driven by Microsoft's antitrust woes, also represents an acknowledgement that the world of open, Web-based applications pushed by Google and others is becoming reality. 

Microsoft says it is publishing today -- for anyone to access free of charge -- 30,000 pages documenting all the APIs and communications protocols that Microsoft products use to connect to Windows Server 2008 and Windows Vista (including the .Net Framework).

In the coming months, Microsoft says, it will begin documenting API and communications protocols for SQL Server 2008, Office 2007, Exchange Server 2007 and Office SharePoint Server 2007. Microsoft plans to finish the project in June and says it will continue to reveal APIs and protocols in subsequent versions of those products.

The company says developers looking for patent-infringement protection for implementations of Microsoft's APIs and protocols would be offered licenses at low royalty rates and under reasonable terms.

Microsoft also says it will design new APIs for Word, Excel and PowerPoint to allow developers to plug in additional document formats and enable users to set those formats as their defaults for saving documents.

In addition, Microsoft will document how it supports various standards and the extensions it makes to those standards.

And finally, the company will launch something called the Open Source Interoperability Initiative, which will consist of a set of labs, plug fests and technical content to ensure that more Microsoft and open source software can work together.

"Microsoft says [opening up APIs] is an acknowledgment that in today's world, many more flowers bloom when platform companies make their APIs completely open for developers to write to, à la Google and Microsoft's recent investee, Facebook," 451 Group analysts Matthew Aslett, John Abbott, Nick Selby, and Vishwanath Venugopalan wrote in their commentary on the announcement.