"[Swift] was initially a proprietary language, but version 2.2 was made open-source software under the Apache License 2.0 on December 3, 2015"

Darwin is also a bad example:

"On July 25, 2006, the OpenDarwin team announced that the project was shutting down, as they felt OpenDarwin had "become a mere hosting facility for Mac OS X related projects", and that the efforts to create a standalone Darwin operating system had failed.[40] They also state: "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."[41]"

"PureDarwin is a project to create a bootable operating system image from Apple's released source code for Darwin.[43] Since the halt of OpenDarwin and the release of bootable images since Darwin 8.x, it has been increasingly difficult to create a full operating system as many components became closed source."

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laserlight 21 minutes ago | parent [-]

What does OpenDarwin or PureDarwin, independent projects, have to do with the fact that Darwin, Apple’s OS kernel, is open source?

	▲	WD-42 6 minutes ago \| parent [-]
		Because they show that Darwin may be technically open source, but Apple are horrible stewards of it. It's impossible to actually build a usable operating system from it, which is probably their intent.