Ya might want to read the entire article, Satcomer...
This is scare tactics on the part of Microsoft. Due to recent court rulings, it's much more difficult to defend software patents because they are based on mathematical algorithms that not easily patentable. I'd venture to guess that Mac OS X was patented way before MSFT's 2002 late entry into the internet/software game.
And whom do you sue for Linux? It's an open source software with hundreds of companies supporting it.
"For a variety of technical reasons, many dispassionate observers suspect that software patents are especially vulnerable to court challenge."
Mac servers are such a small part of the game, and they are much more easily defended because they are hardware based and the software is owned by Apple. Not sure what vulnerabilities Apple has in the scenario put forth by the article?