Apple previously announced its programming language swift is open source and avalible on linux, apple previosly provided many open source projects and many of its core technologies are still closed to apple and those are closed source. Now apple tooks one step towards open source projects by making its most powerful and creative operating systems XNU kernel source codenof both iOS and macOS open source and Source code is available on GitHub.
XNU is the kernel of computer operating system which is developed and maintained by Apple Inc. since December 1996 for macOS and available as open source software for Darwin OS, and XNU means X is not Unix.
By providing this source code to developers as open source, now developers will understand core part of macOS kernel and it is easy for them to learn how devices and layers of operating system works. By making macOS kernel source code open source apple attracted many developers as well as developers also deeply bind upcoming applications more tightly with them.
Source code is provided with Apple Public Source Licence 2.0, which is restrictive license; you can download this source code on github and understand how that code exactly works and what is core components of macOS and iOS.
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