@KeyJ I'm not sure why @aeva thought of your post as "dogshit". You're right here. First, Mozilla code is licensed under the MPL, compared to the more permissive 3-clause BSD license of Chromium. So this makes the latter a more attractive option legally, because there's just less legal headaches to worry about.
Second, Mozilla has never successfully managed to get their Gecko engine to be embeddable unlike Blink. They've tried for many years (remember XULrunner?). I'm not really 100% sure why, maybe Mozilla is so damn lazy in writing documentation (this is one of XUL's problems after all), or maybe they overextended (they also worked on FirefoxOS), idk. But I can say for sure that to this day we are still living with the consequences of this failed experiment by Mozilla, as someone who used to actively contribute to one of Mozilla's forks (Goanna, whose latest and final iteration hard-forked from 52.9.0).
If "libxul" makes you cry in despair you will know what I'm talking about. I tried everything I can to decouple the third-party media code from this awful monolithic library (which became a thing because Mozilla thought it would be easy to embed Gecko if everything is put inside a single huge library) in non-Windows, but it's just giving me linker issues after linker issues. I don't fucking know why. Maybe it's their equally as godawful Python-based build system in fault. Maybe it's the linker. Or maybe I'm just the one at fault here. I don't know and I don't want to know at this point.
Working with Mozilla code is just a horrible experience. I don't regret working with Pale Moon and the whole UXP umbrella, mind you (they're great people and people should contribute to them instead of Mozilla!), but there's just a point where you have to say "screw it" and just stop fixing some goddamn incompetent organization's mistakes from years, no even decades ago.