Huh, interesting. Is it that you're avoiding Mozilla from some sort of retribution, preventing you from effectively working on Waterfox in case you anger them? I'm not sure it should matter too much what Mozilla thinks about other browsers comparing themselves to Firefox, it's definitely fair usage as long as you don't try to trick people into believing Mozilla is also building Waterfox / Waterfox is somehow exactly the same as Firefox.

Just adding Firefox in your comparison table really should be fine, and kind of makes me want to ask someone at Mozilla why others would be afraid of doing so.