Nowhere in the GPL does it say how you can USE the software - you are free to run, modify, and use it any way you see fit. All its restrictions are triggered by DISTRIBUTION of the software, especially modified versions.
The big gotcha is what one understands under the word "use". If I want to USE it as a basis for my business where I sell routers with the GPL software, there are some tiny restrictions regarding that, as Linksys learned [0].
That’s correct. You can’t take freedoms away from your downstream users. As I said before, violating a free software license usually means you are stealing from your users, negating them rights they ought to be given.
That’s one semantic interpretation of “use”, but not the only or the obvious one.
For most physical objects and concepts, distribution isn’t a subset of use. e.g. the post office. You can be a user, but you have no ability to distribute the post office - because that’s not a thing that is possible or makes sense. In that case distribution is not a subset of use. Other examples: most saas, e.g. gmail. Good luck distributing gmail.
[0] https://en.wikipedia.org/wiki/OpenWrt (see History section)