"All this stuff is up for grabs," Updegrove said. "What a court would say is always different. I don't think anyone can look you in the eye and say, 'If this went to court, I can guarantee you how this will play out.'"

Such a dispute might never get to the point of quibbling over legal definitions, Updegrove added, because of the history of OS patents. As others have noted, he pointed out that Linux is "Unix warmed over," and Unix has been around much longer than Windows. Microsoft theoretically has had plenty of time to its exercise patent rights since Linux was first created but has not, though even its right to do so is unclear because the company will not publicly disclose which patents are being violated.

"When do they decide to wake up in the morning and say they have rights today that they didn't have five years ago, 10 years ago ... 20 years ago?" Updegrove asked. "Nothing has changed to give them any rights now."

Furthermore, Apple or IBM -- anyone who owns an OS, for that matter -- would have just as much right to sue for patents as Microsoft does because all of those companies have patented OS technology that has been used broadly over the years, he said.