Lindsay cited open-source projects and companies such as Google Inc. as the sources of most innovation in the last several years, and said Microsoft has been too slow to adopt new business models other companies have used to move the technology industry forward. "Their business model is fundamentally changing and Microsoft is using the courthouse to extend their old way of doing business," he said.

Zemlin was more blunt, calling Microsoft's "posturing" as "empty threats from a scared giant whose monopoly is being challenged."

Charles Merriam, an independent consultant and entrepreneur in Saratoga, California, who uses OpenOffice.org and Open Source Linux Desktop rather than Microsoft Office and Windows, also suggested that Microsoft is feeling the pressure from more nimble competitors, and is trying to cover its own inability to compete by attacking competitors. "It's just like with SCO Group -- when they no longer had a product to sell, it started suing people," he said. "It looks like Microsoft is throwing in the towel on trying to be innovative."

However, Merriam said that while larger companies are less likely to worry about Microsoft's threats, some startups might be afraid that the company could sink their businesses by suing for patents, and may consider moving offshore to escape possible litigation.

China Martens in Boston and Robert Mullins in San Francisco contributed to this article.