Some of the more "commercial" versions of Linux are doing the "per seat" thing as well although generally at a cost that's much less than M$.But the nice thing is that with so many Linux distros available you can choose between somewhat easier "commercial" versions that may have somewhat stricter licensing conditions and somewhat "geekier" totally free versions.
If you are a little more "tech savvy" and aren't afraid to spend a bit of time and learn, you can save piles of money on operating systems (and applications) which is a tremendous bonus for individuals, small businesses, community organizations and in developing countries.
You can also keep your old hardware up and running for longer periods of time. You're not "forced" to upgrade your hardware just to run the latest M$ operating system.
Although I haven't seen the specs yet, my understanding is that when M$ releases their "Longhorn" operating system sometime in 2006 it will require hardware that most folks don't even have yet to get any kind of decent performance out of it.
So folks will be back on the "treadmill" of hardware upgrades.
I think this will create quite an opening for Linux on the desktop.
What's holding Linux back on the desktop (in the home) I think is a) lack of games and b) the amount of software piracy.
Much as M$ complains about software piracy it actually helps them maintain their monopoly. Folks will tell you "Hey why would I want to put Open Office on my computer. My Microsoft Office was free (nudge nudge wink wink)."