Stephan Richter wrote:
Anything you build on top of lovely.rating can be ZPL, since schooltool.requirement is used as a library that is not extended.

I do not understand how "is used as a library that is not extended" affects matters? Using a GPL-ed component as a library without extending it doesn't mean I can stop worrying about the GPL when using it in a larger program, as far as I understand.

What you say is true though: anything built on top of a GPL-ed package can be ZPL.

There is a 'but' here though, and this has to do with expectations and the underlying reasons the ZPL is the license of the Zope repository and people tend to be careful about GPL-ed stuff.

I think the provisions of the GPL state that anything that links to a GPL-ed component will need to be distributable under the terms of the GPL:

"These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it."

So, in my I'm-not-a-lawyer-thank-goodness reading, that means that if I distribute software with a GPL-ed component in it, I need to distribute all the components in this under the provision of the GPL as well. This additional stuff can indeed be ZPL, but since GPL is in there, I cannot distribute proprietary code that uses this software stack, unless I rip out the GPL dependency first. That is, if I give my code to someone, I must give them the source code of everything involved, and they can give that source code to anyone they like, under the provisions of the GPL.

The expectation one may have of a ZPL-ed codebase is that it is useable even in proprietary settings without having to comply to the rules of the GPL. This is not the case for a ZPL-ed component which relies on a GPL-ed component.

Whether one considers this right, proper or fair is another debate I do not want to go into.


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