Licensing: GPL 2.0 and sideloading

[petersamokhin]

https://github.com/kohler/gifsicle/blob/338d286490750a4cc1ba728ddd4588bf46027ff7/README.md?plain=1#L108C33-L112C35

Developers or distributors who plan to use Gifsicle code, whole or in part, in a product whose source code will not be made available to the end user -- more precisely, in a context which would violate the GPL -- MUST contact the author and obtain permission before doing so.

Hello there! I would like to clarify this particular paragraph.
I understand that only the license text is legally binding but I believe it still makes sense to explicitly discuss it with the owners.

GPL 2.0 enforces disclosing the source code only in case of "derivative works".
The term "derivative works" is quite explicit and usually it means embedding the binaries of GPL2-licensed code, or using it as a library in the code, or similar.

But, if even a closed-source paid software just downloads a pre-built binary (e.g. from Github releases) and calls it via CLI, it should not violate GPL 2.0, as far as this usage is properly attributed: this is what a quick research confirms, and what FFmpeg maintainers confirmed (FFmpeg and related GPL-licensed libs like libx264 all use GPL 2.0 too).

This is different from AGPL or GPL 3.0 because they don't narrow the scope, don't use terms like "derivative" and use more broad terms like "...work based on...", so "sideloading binaries and calling them via CLI" can fall there.

I don't think it makes sense to alter README, but for sake of public visibility, it'd be great if you can confirm that you are happy with the above-described use-cases and won't consider such cases a violation.

Cheers!