> А почему эппловское ядро не используется в альтернативных ОС?

Возможно, потому что не всем нравится игра "... а сегодня мы передумали и закрыли код, сосите, э-э, лапу".

https://web.archive.org/web/20010606213907/http://www.openso...
> Through the open source model, Apple engineers and the open source community collaborate to create better, faster and more reliable products for our users.

https://web.archive.org/web/20020601072805/http://developer....
> Apple's open source projects allow developers to customize and enhance key Apple software.
> Through the open source model, Apple engineers and the open source community collaborate to create better, faster and more reliable products

http://www.macworld.co.uk/news/mac/apple-closes-down-os-x-14663/
> Apple says that the state of an OS X-compatible open source x86 Darwin kernel is "in flux."

http://web.archive.org/web/20060804104416/http://opendarwin.org/
> Over the past few years, OpenDarwin has become a mere hosting facility for Mac OS X related projects.
> The original notions of developing the Mac OS X and Darwin sources has not panned out.
> Availability of sources, interaction with Apple representatives, difficulty building and tracking sources, and a lack of interest from the community have all contributed to this. Administering a system to host other people's projects is not what the remaining OpenDarwin contributors had signed up for
>