[PyQt] A nasty licencing question

[David Boddie]

On Mon Jul 30 10:23:50 BST 2018, Sampsa Riikonen wrote:
> On 30.07.2018 12:16, David Boddie wrote:

> > How does apply to the scripts you were talking about? Sure, the combined
> > work is now licensed under the GPL but the original scripts can still be
> > obtained from outside the combined work and are still MIT licensed.

I was being a bit careless with words. I meant "snippets" rather than
"scripts", but your questions below are still valid. In my mind they are
different things, but that's not important here. :-)

> What do you mean David..?
> 
> Do you mean if you remove "from PyQt5 import .." then that's "outside
> combined work" and thus is not anymore GPL licensed?

No, if you obtain something licensed under the GPL then changing the module
dependencies isn't going to change its license.

However, I don't exactly know how things work legally if you obtain a program
which is a collection of files (executable, modules, etc.) and some files
contain MIT license text, others GPL license text, and so on, then you want
to redistribute parts of it.

If there is a file with an MIT license in that combined work that you want
to redistribute then it will still have its original license text. I don't
see why it couldn't be distributed again under its original license.
However, if it was modified by the person who supplied the combined work
then perhaps those modifications would be licensed under the license of the
combined work, so you couldn't redistribute it under the MIT license again,
though I'm not sure I've ever seen something like that.

I think the core issue here is that, if person A uses a snippet to create a
combined work and distributes it under the GPL (or the LGPL for that matter)
then whoever receives it needs to get the rights those licenses grant them.
If person B instead extracts the snippet from the combined work and creates a
closed version then they have to show that the snippet was obtained under the
MIT license. If the snippet was modified by person A to the extent that they
hold copyright on parts of it then person B may not be able to show that and
there could be a license incompatibility.

This is based on my incomplete understanding of how licenses interact in
combined works. I'd like to see a description of how projects with multiple
licenses handle situations like these - links anyone?

David