Prophet,
there's no stealing involved here. the Freetrack guys probably asked for a copy of the trackir sdk here:
http://www.naturalpoint.com/trackir/05-developers/developers-pc-game-simulation-sdk.html
from there, building up your own code to mimic the same trackir API isn't too hard. It's really the way open source implementations of all kinds of proprietary software happen and it's not illegal. The openoffice/word comparison isn't too far off track. I wouldn't say it's apples to oranges at all.
As far as IP goes, naturalpoint didn't invent head tracking, they were just the first (as far as I know of) to make a solid, working consumer product out of it. It was inevitable that someone else would make software to do the same thing and then give instructions on how to make the hardware.
Naturalpoint has two options here... make a product that's so much better than what hobbyists can do on their own that people buy it, or try and block the competition out by closing up their interface and playing hardball with game developers. Unfortunately, they appear to have chosen the latter and that never works. Remember 3dfx and Glide? Remember when the good people at AOL kept trying to make the AIM protocol impossible to talk to with jabber etc? Everybody gives up eventually... the smart ones figure out a way to make a buck off having a bunch of new users who weren't interested in their original product.
I'd like to see Naturalpoint start selling just their hardware for use with freetrack at a lower cost. I have to assume they spend a lot of resources messing with the software (support, etc) that they could let the freetrack guys or the open source community at large deal with and focus on the cameras and clips.
sbern.
ps. I get 100 fps with my wiimote freetrack setup and it's really low latency..