Greenpeace is a (non-profit) corporation. Unions are corporations. Municipalities. Colleges and universities.

* https://en.wikipedia.org/wiki/Legal_person

Should they have to pay?

From 2010 to February 2024, it was sponsored by Quest Software according to the history page[2].

[1] https://github.com/sudo-project/sudo/blob/main/LICENSE.md

[2] https://www.sudo.ws/about/history/

After all, people in these companies don't work for free and are able to spend a lot of money for other services.

Say, I clone sudo. Clearly, a human applying freedom zero. I use it in my projects. Probably still freedom zero. I use it in my CI pipeline for the stuff that makes me money... corporation or human? If it's corporation, what if I sponsor a not-for-profit that provides that piece of CI infra?

The problem is that "corporation or not" has more shades than you can reasonably account for. And, worse, the cost of accounting for it is more than any volunteer wants to shoulder.

Even if this were a hard and legally enforceable rule, what individual maintainer wants to sue a company with a legal department?

What could work is a large collective that licenses free software with the explicit goal of extracting money from corporate users and distributing it to authors. Maybe.