GNU GPL is a fine license for GNU/Linux distributions, and I don't hold venom toward it. Trust me, I get why people would feel it's fair to codify giving back like they were given to.

However, I don't share the position of the FSF regarding copyleft and permissive licenses. Freedom involves the ability for someone to not do the right thing. And I guess the way that *BSD and other permissively licensed projects might see it, is that it is akin to an honor system. Old newspaper machines had an honor system for taking one newspaper after putting the money in. Certain people did cheat this, but it was a minority of people.

*BSD projects place everything under a permissive license, hoping people will choose to do the right thing and contribute back. This actually happens a great deal of the time, even when for selfish reasons like Apple and others wanting them to keep contributing code.

So Apple made improvements to things like cups and also released clang, which is a superior compiler in some ways compared to gcc.

People will point to the success of GNU/Linux in contrast to *BSD systems, but forget that in the early to mid 90s, there were lawsuits involved that made people scared to contribute to BSD. Developers went to GNU/Linux, because the code wasn't in legal dispute. Linus Torvalds himself said that if either 386BSD or HURD (kernel) were ready at the time, he likely wouldn't have made the Linux kernel.