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AirPods and AirPower: Everything We Know
Intel (x86) OS X Kernel Becoming Closed-Source?
Apple's Open-Darwin mailing list has an ongoing discussion in which some users point out that Apple has actually not released the XNU source for Intel since 10.4.3 or perhaps earlier. Therefore, it appears as though the facts of the article are not new, but rather are just now gaining press attention.
Apple has not officially commented on the future of XNU's source availability, and it appears most conclusions as to why the source has not been released is based on speculation rather than inside knowledge.