> "how can they do that?"
License future important libraries only for use via their cloud toolchain?
Stop contributing support to non-cloud toolchain and/or intentionally break it?
Slip more restrictive licensing into new easy to use features (like a vision service) that taint combined products?
Never underestimate a company's ability to pay lawyers to restrict freedom.
The issue with that is that they don't even own the (exclusive) rights to "their" libraries. They are nothing more than a package repository.
How? Libraries are all open source by the community. Arduino AVR doesn't need proprietary microcode to boot= and run.
Last Arduino I worked with is one of those ARMs that pretend they're an AVR, for example.