I'm hesitant to build on a platform that could be appropriated by corporate interests. An example of this is the way Apple has appropriated BSD for MacOS. The BSD code is still open, but the tooling and funding comes from Apple to an extent which allows Apple to determine the direction to some extent.

I have no problem with MIT for smaller tools, but the compiler is too foundational a dependency to take risks on, and it needs better protections--protections which are afforded by the GPL and the FSF's funding of GNU projects.