If you are just calling the service through it's API (either CLI or through the programming language interface), then you don't need to distribute anything.
This just protects against people taking open source code GPL, modifying it for themselves, using it in backend services, and then never distributing their modifications.
That's contestable afaik.
> through the programming language interface
i.e. dynamically linking which is usually understood to be prohibited unless linking code has a compatible license.
> either CLI
Here's the problem - you can take any GPL library, make small CLI or REST adapter for it and license it GPL as well, then use that adapter from your proprietary application - is that still allowed? Because if it is then GPL can't ever be enforced and if it isn't you can't call CLI APIs even if original libraries themselves provide it.
However, I think if you just installed Pijul on a server and then called it through your operating system interface, then you _might_ be fine. You might need to make it so the interface to Pijul is generic and could swap out with other VC systems.
I still might also be wrong about this. I'm not a lawyer and the comments in [0] are on both sides of the argument.
[0] http://softwareengineering.stackexchange.com/questions/10788...
EDIT: edited to express less certainty over my interpretation of the license
Might, exactly. Depending on various courts accepting there is a loophole in GPL, and my layman understanding is that there isn't. Skimming GPLv2 I don't see them differentiating in derivative works between those that use compile time linking and those that use mechanisms like CLI. I'm weary of bringing after the fact constructs to justify something that GPL doesn't talk about. And after all how is CLI that much more different than dynamic linking - CLI is merely an interface that is subjectively a bit more friendly in certain situations but this imo shouldn't a have a bearing in legal discussions.
afaik this means any kind of linking (static or dynamic), using a jar or using a npm package or similar..
>through the programming language interface
which implies some version of the above