This dispute was running prior to the release of OSX. Apple subsequently made concessions to the issues mentioned. You can view an opinion of the remaining issues here: APSL
This is not really an OSX thing, it's about GNU-Darwin. You can download Darwin from Apple, there is a version for PPC and x86.
It helps if you understand what "Free Software" means; it does not mean free as in you don't pay for it. It's a philosophy of software development, modification and use that allows people to freely modify the code and in general you should post your code so others can also offer feedback and modifications.
For example, Apple's license says you *must* post your mods to Apple if you intend to use modified Darwin code devoped for in-house (not public) use.
Apple also has provisions in the license to partly guard against being sued if someone posts proprietary code that somehow ends up in the distribution at a later date.
These provisions are not strictly in agreement with what most free software licenses say, hence his dismay.
I think this guy is getting a little too worked up over it, but that's just my opinion. Most UNIX ports that run in Darwin are done by the usual army of Fanatical MacHeads, and he doesn't count himself amonst them.
Not really something to worry about; somebody somewhere will take up the slack if he quits.