Anything using either "Fire" or "fox" in the name is infringing on Mozilla's registered trademark by naming it too similarly.
Really? Trademark law is not so specific. "Too similar" is entirely open to court's interpretation.
Though if I were a judge, I would probably find Waterfox infringing too.
Right. The IANAL
acronym is important here.
The (admittedly vague) breakdown from cases I've followed is that if there is a chance that it could create confusion, its violating the law. Changing the icon color and the first part of the word of the program seems a bad way to declare a difference. Despite this, it is up to the intellectual property holder to move on this, which they certainly could. If Pepsi and Coke can both copyright individual colors and Chick-Fil-A can own the phrase
"eat more ___" then I think Mozilla has an asteroid-proof case here.
For reasons I've gone into before
, Mozilla is not and probably will not be litigious in this regard. Ask Oracle what developing a reputation for taking things to court has done for their PR. Fortunately there's a built-in balancing factor here: Waterfox is also subject to a community and that's very likely where this will all get worked out.