People in the Linux community are asking Microsoft to "show me the patents." Microsoft is certainly creating some uncertainty but they are very likely on solid footing on some of their many patents. The reason that Microsoft isn't making a move is because it's not yet clear who to go after. The desktops? The distributions? The corporations deploying the software? A legal battle would likely cost them more then they could gain.
Many of the patents in the MS portfolio cover core design and implementation details that would not be trivial to code arround. Three examples that I suspect are undoubtably part of the list:
- The start menu
- Long file names
- Plug and Play
Each of these covers a different area of design and protection. The start menu is clearly a distinct visual element that is very recognizable as a fundemental part of windows.
Long file names is a level deeper in the OS. This describes how a file can have spaces and still be used to traverse folders using traditional commands with quotation marks. The use of quotation marks is not-obvious and the duplication of the feature (even though it's a separate implementation) is likely an infringement.
Lastly Plug and Play is down in the guts of the OS. This is core to how the OS deals with hardware devices. In order for Linux to be compatible with hardware it's necessary to be compatible with the way that Windows does plug and play.
Of course this is likely the tip of the iceberg. Hundreds if not thousands of additional patents lie just beneath the surface.
The best defense is a good offense
There are many technologies that are invented and created by individuals in the open source community. These technologies are invented, designed and made popular. Many of these inventions make their way into Linux and other products. The best defense is to build up an 'open patent portfolio.' This would allows contributors (IBM, Dell, Novel, Adobe, Ubuntu, KDE, Gnome, etc.) to include patents in a community portfolio. The portfolio would be open and cross-licensed to other organizations that provide reciprical agreements.
Basically companies can use the open patent portfolio without cost as long as they don't sue the patent contributors.
What ends up happening is you have a 'cold war' on patents. Both sides build up an arsenal of 100's of patents and neither side will sue because it's a no win situation.
(A crazier idea is to enact software patent reform, but that's just pie-in-the-sky long-term thinking.)