When Apple got in to Open Source in the 2000s, they defined it as:

>"The basic principle is to involve as many people as possible in writing and debugging code, by publishing the source code and encouraging the formation of a large community of developers who will submit modifications and enhancements." [0]

Apple's use of open source was eye-opening to me. I liked Darwin, and watching it sadly go extinct was a weird bummer.

>As of January 2023, Apple no longer mentions Darwin by name on its Open Source website and only publishes an incomplete collection of open-source projects relating to macOS and iOS. [1]

I think the simplest answer is anything based on the Debian Free Software Guidelines:

√ Free redistribution √ Inclusion of source code. √ Allowing for modifications and derived works. √ Integrity of the author's source code (as a compromise). √ No discrimination against persons or groups. √ No discrimination against fields of endeavor, like commercial use. √ The license needs to apply to all to whom the program is redistributed. √ License must not be specific to a product. √ License must not restrict other software.

[0] https://web.archive.org/web/20000901055855/http://www.openso... [1] https://en.wikipedia.org/wiki/Darwin_(operating_system) [2] https://en.wikipedia.org/wiki/Debian_Free_Software_Guideline...