The BSD License Means Companies Don't Contribute Back
The BSD license means that you can take the code in FreeBSD and do whatever you want with it, as long as you don't sue us or pretend that you wrote it. Without the legal obligation to share code, it is possible to use FreeBSD code almost anywhere. Some companies, almost certainly, will take our code, modify it, and never give anything back. They are free to do this, however many don't.
Consider, for example, the case of two major Internet companies: Google and Yahoo! The former bases their internal infrastructure on a GPL'd operating system, while the latter uses FreeBSD. Because Google does not distribute their modified operating system, they can keep things like the GoogleFS private. In cases like this, where software is developed for in-house use, there are no differences in the requirement to share changes between the two licenses. There are, however, some issues with linking that mean that, for example, a GPL'd library can't be used where a BSD licensed one could be.
A lot of companies have made significant contributions to FreeBSD over the years. They don't (usually) do this out of a sense of altruism or as a result of legal threats, but out of the most dependable of motives: self interest. Maintaining a fork of any project, especially one that is developed as quickly as FreeBSD, is expensive. Pushing changes upstream is a lot cheaper. If there are changes that are useful to a wider community and not core to their own business interests, then it's cheaper to publish them and reduce the maintenance cost of the fork than to keep them private.
> В таком виде — вызывающе ложная информация. Никакая свободная лицензия не может обязывать вас с кем-то *делиться усовершенствованиями*.
Интересна ваша правильная формулировка
;)