When it released Swift as open source, Apple made a rather contentious claim that it was the first major computer company to make Open Source development a key part of its ongoing software strategy.
That sparked both a Tweet-storm and a change of heart, with Cupertino revising the marketing-speak to read that Open source software is at the heart of Apple platforms and developer tools (true, ever since it bet on FreeBSD**), and Apple continues to contribute and release significant quantities of open source code (others do more*, but what the hell).
The source code directory for OS X 10.11 is here, and the kernel is here.
Given the widespread lack of interest in actually doing much with the Darwin source code, the release is as much an intellectual curiosity as anything else. Swift, on the other hand, seems to have a much sunnier future.
* To be fair, the full Apple open source list, here, is pretty decent. And if you're quick, you can still see Cupertino's original "first major computer company" wording there, which El Reg is sure will get edited soon.
** This originally read "OpenBSD". Like John Cleese in A Fish Called Wanda, the author is very, very, very, very, very, very sorry.
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