Licensing

PureDarwin is not under one licence. It is Apple’s open source under the APSL, plus BSD-licensed code from FreeBSD, plus MIT-licensed work from other projects, plus code written here. That is normal for a system of this shape, but it means “what licence is PureDarwin” has no single answer, and anyone packaging or redistributing it needs the detail.

This page is an orientation, not a legal opinion. The authority is always the header on the file in front of you.

The broad shape

Foundation is worth a note. It contains MPL 2.0 code, and the project treats the whole component as MPL. That is a working convention rather than a strict consequence of the mixture: handling it uniformly keeps merging straightforward, and contributors are encouraged to do the same. It is a choice made here, not something the licence imposes.

XPC, in detail

src/Libraries/XPC is the clearest example of why a single answer does not work. It is one directory holding components under different terms:

There is no aggregate licence for the directory. Collecting differently licensed components in one place does not give them shared terms, so each of the above keeps its own, and the SPDX header on the file in front of you is what governs it.

PD 1.0 is the project’s own licence, a BSD-2-Clause derivative; the text is in PUREDARWIN_LICENSE.txt at the root of the repository.

corecrypto is the exception

The corecrypto kext and the CommonCrypto pieces above it are GPL, and unlike the other GPL software the project uses they are part of the default build. That is not a choice made on the merits: Apple’s own corecrypto is not usable here, and the code descends from rafirafi’s 2016 pdcrypto with tiny-AES128-C adapted into it, which is what existed at the time.

If you are redistributing PureDarwin, this is the licence to know about. Replacing it is on the roadmap.

Published by Apple is not the same as licensed

Some source Apple has published carries no usable licence grant. The pattern is a repository where only some files have a per-file licence header and there is no repository-wide LICENSE, which leaves everything unheaded with nothing attached to it.

CommonCrypto is the example that costs the project most: it is published, it is exactly what we want, and the unheaded parts cannot be used. That is why corecrypto here is a GPL descendant rather than Apple’s own code.

Apple’s libDER arrived with the same gap. That one had a better ending: rather than work around it, the project’s libDER was written here, and is PD 1.0 as a result.

Check licensing file by file before building a port around an Apple component. Finding out late is expensive, because by then somebody has read the code.

Code kept outside the tree

The project avoids folding another independently licensed substantial component into the default distribution when keeping it external works just as well.

fbDOOM is the working example. It is GPL, so rather than living in the tree as a flake input it is an external checkout, pointed at by PUREDARWIN_FBDOOM_SOURCE_ENV and built with --impure. This is not an objection to the GPL: a GPL component in the tree brings obligations that then apply to everyone packaging or redistributing PureDarwin, and keeping it opt-in means the default build has one less licence to reason about while people who want fbDOOM can still have it.

If you need to add something that must remain external, copy the fbDOOM shape. The principle is not specific to the GPL; ZFS, under the CDDL, is the other obvious candidate.

Contributing

What the project can accept, and the clean-room rules for writing drivers from datasheets, are in Contributing and in CONTRIBUTING.md. The short version: every contribution has to be yours to give under a compatible licence, and code whose licensing is unknown cannot be accepted or even looked at.