As part of the effort, the two companies will jointly contribute to the development of a new version of Apache POI -- an open source, Java application programming interface for accessing and managing Office's binary formats.
Microsoft said Tuesday that the goal is to make it easier for open source developers to write programs that are compatible with Microsoft's Office Open XML format, which is the default format for Office 2007 applications such as Word, PowerPoint, and Excel.
"Donating code to an established, consensus-driven organization such as the Apache Software Foundation benefits both our customers and the open source community at large," said Sam Ramji, senior director of platform technology strategy at Microsoft, in a statement.
Microsoft appears to want to mend its relationship with developers of open source software, which company CEO Steve Ballmer once called "a cancer."
The company in February said it would 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 said it would 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.
Some analysts believe Microsoft's recent commitments arise from practical considerations rather than any newfound love for the open source community.
The company is hoping to build support for its effort to have OOXML recognized as a standard by the International Organization for Standardization. Voting by individual member nations on the issue is slated to wrap up this month.
Microsoft is also looking to appease antitrust bodies that continue to accuse the company of using monopolistic practices to bolster its market position.
EU regulators last month slapped the company with a record $1.35 billion fine.