They contribute some things, sure. But the also don't contribute some things. It is hard to know how much because it's kept secret from all of us, even their own customers.
> "It's not like the Rust compiler is proprietary software with their own closed-source fork of LLVM..."
Rust no, hut there are a lot of proprietary, semi-incompatible proprietary forks out there.
One of the reasons that LLVM has been able to evolve so quickly is because of all the corporate contribution it gets.
GCC users want Clang/LLVM users to know how dumb they are for taking advantage of all the voluntary corporate investment in Clang/LLVM because, if you just used GCC instead, corporate contributions would be involuntary.
The GPL teaches us that we are not really free unless we have taken choice away from the developers and contributors who provide the code we use. This is the “fifth freedom”.
The “four freedoms” that the Free Software Foundation talks about are all provided by MIT and BSD. Those only represent “partial freedom”.
Only the GPL makes you “fully free” by providing the “fifth freedom”—-freedom to claim ownership over code other people will write in the future.
Sure, the “other people” are less free. But that is the price that needs to be paid for our freedom. Proper freedom (“full freedom”) is always rooted in the subjugation of others.
I think that's the core difference.
But hey, if you try hard to be nice to your master and do not demand anything, for sure they will always treat you well!