Firefox, its logo, etc are trademarked and therefore restrictions apply when re-distributing, and that has been the case for as long as I remember. There’s nothing stopping you from compiling it yourself, calling it Firefox, or using their branding, as long as you don’t redistribute your build and modifications to others while still using their branding.

I switched from proton to tuta back when Yen started praising Trump. It told me everything I needed to know about him.