The Linux Foundation is prepared to defend any Linux user charged with violating Microsoft's patents, but executive director Jim Zemlin said that a critical review of Windows code would show that it can be claimed to violate other vendors' patents as well.

"If you use Windows, Solaris, [IBM's] AIX or any similar operating system, you have the same patent infringement risk as using Linux. Microsoft should be careful of what it starts because it doesn't know where it will end," said Zemlin in an interview. Zemlin heads the organization that resulted when the Open Source Development Labs merged with the Free Standards Group in January. Both groups aided targets of the SCO Group, when it filed suit against Linux users AutoZone.com and DaimlerChrysler. SCO later dropped the AutoZone suit.

"Who are they going to sue? Companies will not continue to do business with suppliers who sue them," said Zemlin.

Microsoft carefully avoided threatening to sue any Linux users while nevertheless maintaining in a Fortune article today that 235 of its patents are violated by various forms of open source code. Sun's Open Office suite allegedly violated 45 of Microsoft patents, while the Linux kernel allegedly violates 42 patents. Linux graphical user interfaces violated another 65, Microsoft's general counsel Brad Smith and chief of licensing Horacio Gutierrez stated in the Fortune story.

Zemlin noted that Microsoft continues to decline to name the patents allegedly violated, which would let knowledgeable opinion to assess its claims. It also may have never tested its patents in court. Holding a patent doesn't guarantee victory in a patent dispute. The patent needs to be upheld in a court case as covering a unique work.

"Claiming violations of untested patents is a lot different from claiming violations of court tested patents," he said.

The Microsoft statements are meant to preserve Microsoft's Windows and Office desktop monopolies, "the greatest cash cow ever created," he asserted. By keeping as many people as possible for considering alternatives, Microsoft is protecting a business that yields $34 million a day to its coffers, Zemlin said.

"Look at SCO or any other patent troll out there. It's nutty to think you can sue your customers and keep their business," he said.