Former Sun Microsystems CEO Jonathan Schwartz this week said he understands how Google must feel in the wake of Apple's patent-infringement lawsuit against Android phone maker HTC. As it turns out, Apple CEO Steve Jobs threatened to sue him as well. So did Microsoft.

"In 2003, after I unveiled a prototype Linux desktop called Project Looking Glass, Steve [Jobs] called my office to let me know the graphical effects were 'stepping all over Apple's [intellectual property]'," Schwartz wrote in his blog. "If we moved forward to commercialize it," Jobs allegedly told Schwartz, "I'll just sue you."

Not so fast, Schwartz warned Jobs. He noted that Apple's Keynote presentation tool clearly used intellectual property that Schwartz's previous company had developed for NeXT, the company Jobs left when he was forced out of Apple in the 1980s. "And last I checked, MacOS is now built on UNIX. I think Sun has a few OS patents, too."

Jobs, he says, was silent. But the important bit was that Apple didn't sue. And according to industry experts, that is often how intellectual property works. Companies line up patents so that they can use them as leverage against other companies. So, if the threat of a lawsuit emerges, a company can point out potential legal issues with its own products as well.

"Bluster and threat are commonplace in business," Schwartz writes. "Especially the technology business."

Jobs wasn't the only high-profile technology executive to threaten Sun. Later, Microsoft's Bill Gates and Steve Ballmer arrived in Schwartz's Silicon Valley office to discuss OpenOffice.org, Sun's open-source office-productivity solution. "Microsoft owns the office-productivity market, and our patents read all over OpenOffice," Gates apparently told Schwartz, telling him that Sun would have pay Microsoft a licensing fee for each copy of OpenOffice it gave away. (OpenOffice is free.)

Likening this deal to a "digital version of a protection racket," Schwartz declined, and noted that Microsoft's .NET programming environment was "trampling all over a huge number of Java patents." He suggested that Microsoft could then, in turn, pay Sun a licensing fee for each copy of Windows it sold, since the .NET environment ships in Microsoft's OS.

Gates demurred, noting that royalties didn't fit in the Windows business model. "It was a short meeting," Schwartz said.

Ruminating over his experiences, Schwartz looks at the current patent litigation situation—in addition to the Apple/HTC spat, Nokia and Apple are also suing each other—and notes that relying on the courts with frivolous litigation is an act of desperation. "Suing a competitor typically makes them more relevant, not less," he adds. "Apple's actions are enhancing developer interest in Google's Android platform."