I think your point is that copyleft creates extra value because those extending it are incentivized to contribute their extensions. But in the case of gcc as co

I think your point is that copyleft creates extra value because those extending it are incentivized to contribute their extensions. But in the case of gcc as compared to llvm, permissive licensing looks to be at least as successful. An issue with copyleft that you need to commit to providing the source beforehand. If you are allowed to choose afterwards, you don’t need to ask in advance, and it’s easier to make the case that upstreaming your patches is in the organization’s best interest. And yes I know copyleft only requires only providing code to your users, but in practice the organization assumes that means the distribution can’t be enforced.