> How do you steal Open Source? Can Pruse no longer use it themselves or something? Sounds wrong calling "companies creating products from other projects" stealing when the intention from the beginning is that others can freely use the created project for whatever.
Thing is, the fundamentals of Open Source have changed over the last decades - and the assumptions people made Back Then no longer hold. Let me expand a bit:
Back in the late 80s and 90s, up until the early '00s a lot of popular open source software was developed by academic institutions or with scientific grants. For them, it didn't matter - the money way paid for anyway and sharing source code fits with the ideals of science. In some projects it's very clear that they have an academic history - my to-go example is OpenStack, the myriads of knobs it has absorbed over the years all come from universities wishing to integrate whatever leftover hardware they had.
But ever since academic funding all but dried up, life has gotten difficult. We got a few rockstar projects that manage to survive independently (cURL), godknowshow (OpenSSL), with consulting services (sqlite with their commercial comprehensive test suite, mysql, mariadb, psql), on corporate contributions (Linux kernel, ReactJS/Facebook), on donations (everything in the FOSS graveyard better known as Apache) or, like Prusa, on hardware they sell. The general idea behind many projects is the implicit assumption: if you use a project commercially and the developer has a commercial support platform, be so kind and pay the original developers a bit so they can improve upon the project.
The problem is when juggernauts with deep money pits, be it companies with net market values in the trillions of dollar range or companies being under influence of the CCP, come on the field and take the hard work of others to make money without contributing back either financially or with code. Legally, they are absolutely in the clear, if the project isn't under AGPL, CC-NC or other such terms. ElasticSearch got ripped off that way by AWS for example.
It's not stealing in a traditional sense, but it is breaking the ethos and expectations.