[kmacleod]

And that's not what I mean. I understand the linking issue. What I'm saying is that the GPL does not force or require someone to relicense their code. Their code is theirs. They only have to license the distribution as a whole with the GPL to be GPL compliant.

You can look at any Linux (or BSD) distribution for hundreds of examples of BSD/MIT code linked to GPL code. The BSD/MIT code packages are not "relicensed" as GPL, but the Linux distribution, as a whole, is distributed as GPL.

[teddyh]

I don’t think that’s true. If a program A is a derived work of B, and B is GPL, I don’t think you are allowed to license A as MIT. It’s legally the same as if you’d taken code from B and altered it; you aren’t allowed to license that under MIT, either.

The many examples of MIT/BSD linked to GPL code are, I believe, cases of either:

1. The GPL code using the GNU C library exception, like the GNU C library. Or libraries licensed using the LGPL. Any MIT/BSD code is allowed to link with that, because the exception in the licence explicitly permits it.

2. The link is done at “arm’s length”; i.e. the MIT/BSD is not actually requiring the GPL code, and so is not considered a derived work.

or possibly

3. The GPL code is the code which links to the MIT/BSD code, which is obviously allowed, as the whole thing is then distributable under the GPL.

Do you have any examples where none of these are the case?

For futher information, I suggest reading the GPL FAQ: <https://www.gnu.org/licenses/gpl-faq.html>

[kmacleod]

Your (3) is ssddanbrown's case. The whole must be distributable under the GPL.

Nothing changes with ssddanbrown's repo, license, or anything. At a future time should they "code it out" and substitute another non-GPL library, their code is still MIT.

From the GPL FAQ, emphasis mine:

FAQ (#IfLibraryIsGPL): If a library is released under the GPL (not the LGPL), does that mean that any software which uses it has to be under the GPL or a GPL-compatible license?

A: Yes, because the program actually links to the library. As such, the terms of the GPL apply to the entire combination. The software modules that link with the library may be under various GPL compatible licenses, but the work as a whole must be licensed under the GPL. See also: What does it mean to say a license is “compatible with the GPL”?

Note, "work as a whole" here means the runnable, binary distribution or downloadable. The source that accompanies the downloadable binary may still be in separate archives with their original licenses. Again, this is exactly how Linux distributions work.