You rewrite that library under an MIT license, so now your code can link to that and run. Is your original code still a derivative work?
> You are not required to accept this License, since you have not signed it.
So to answer your question: no, unless you've copied bits of GPL library into your code (or similar that would be judged as a copyright violation).
There's also a crappy situation of Oracle vs Google that made APIs copyrightable, so now it's not entirely clear if your code + your rewrite of library is still yours if it uses an API of the GPL library.
> > You are not required to accept this License, since you have not signed it.
> So to answer your question: no, unless you've copied bits of GPL library into your code (or similar that would be judged as a copyright violation).
Actually that clears a lot up for me, and I'd have considered myself reasonably knowledgeable when it comes to copyright in general; I think I had a few conflicting ideas about what it means to be an original work. Thank you.
Which might happen very easily: one #include and you might be there.
It matters who is doing the rewriting and how they got the code in the first place.
The GPL is emphatically not clear about anything. It's a legal minefield precisely because no one has any idea what it means, and everyone has their own interpretation.
> It matters who is doing the rewriting and how they got the code in the first place.
Well, then,... that's about as clear as mud.
RMS contacted them, and asked them to relicense. They suggested either reimplementing a stub readline-library, or rewriting their line editing code against another lib instead. RMS insisted that they would still be a GPL-derivative, resulting in the current license situation.
I may be misremembering the recount of this, as this was way before my time.
CLISP et al cannot be forced to distribute their code under the GPL. It's their code and their choice; contract law cannot compel someone who has never entered into the contract to do something against their will -- CLISP didn't knowingly distribute GPL code, so that distribution doesn't trigger acceptance of the GPL terms. They just have to make the situation right once they're made aware of the violation.
To comply with the GPL you only need to publish the one specific snapshot of source code you've combined and redistributed with GPL code, but you don't need to permanently relicense your project if it doesn't contain any code you don't have rights to use. The "tainted" version will be granted as GPLed forever, but other earlier or later versions that don't use any GPL code don't have to.
Or you can go the copyright way, and claim it wasn't a copyright violation (because it was a fair use, or non-copyrightable code) or settle the matter in whatever way the law lets you get away with.
https://sourceforge.net/p/clisp/clisp/ci/tip/tree/doc/Why-CLISP-is-under-GPL
So I guess if someone asks you for the source code, you can require them to prove that they actually have a copy of the GPL version, and not the new one.