This looks very nice! Thanks!

I immediately wondered why Magit was not included and appreciate that finding the answer to that required nearly no effort.

Only documentation for Emacs core and Emacs packages will be included, which must satisfy the following requirements:

1. Be licensed under a free documentation license such as the GNU Free Documentation License 1.3, Creative Commons Attribution 4.0 or Creative Commons Attribution-Share-Alike 4.0 License, etc. This EXCLUDES documentation licensed under the GPLv3, as it's incompatible with the GFDL.
2. ...

Point 1. excludes Magit from being included, sadly.

One way of looking at this is that Magit cannot be included because it uses the wrong license for its manual. My view is that Magit isn't included because this project rejects perfectly fine free licenses merely because they are not (primarily) intended for documentation.

Magit once used the FDL license for its manual--so let me explain why I made the pragmatic choice to write a new manual that uses the same license as the code.

The old manual had some serious issues that made considerable improvements necessary. (If I remember correctly) issues included that the manual was very incomplete, contained obsolete information, some parts were mere stubs, unimportant things were described in detail, while important topics were completely missing.

There also were good parts that I wanted to keep but it was clear those existing parts would only make up a fraction of an improved manual. What I would have liked to do was to keep the nice longer parts of the old manual that describe some concept, and seed the other parts with docstrings copied out of the code.

But I couldn't do that because the licenses conflicted and because I was not the author of the old manual I was not free to dual-license the docstrings. I could have tried to contact all the authors of the manual and/or code and ask them to give me permission to relicense/dual-license.

This would have been a lot of work and I came to the conclusion that it would be more productive to discard the old manual completely and start over. This was quite sad and I am sure some nice things got lost as a result.

I got over that quickly because seeding the manual with the docstrings proofed to be a good strategy, but this was still a loss and my main takeaway was that I never wanted that to happen again.

So now the documentation that lives in a separate file and the documentation that is sprinkled across the code both use the same license and I can freely copy in either direction without having to ask anyone to relicense anything.

The FSF can use different (and one may argue "more suitable") licenses for documentation and code because they require that contributors assign their copyright to the FSF. As the copyright holder they can then relicense documentation as they see fit.

IMO the problem is that the FSF does not simply use the incompatible licenses themselves but that they recommend that others in the free software community do the same. For projects that don't require copyright assignments I consider that a huge mistake. Such projects end up constantly violating the licenses they themselves have chosen when they copy across the license border, or they end up writing a lot of documentation twice to avoid doing that.

Imagine a contributor adds a new option, they forget to update the manual, and you overlook that when reviewing the pull-request. Later you notice and ask the contributor to give you permission to copy the docstring to the manual, but they have dropped of the surface of the earth and you get to write the same, yet different documentation from scratch.

So this is why Magit does not use two incompatible licenses. Please consider including manuals that use any free licenses, even licenses that are primarily intended for code.

Cheers,
Jonas