Firefox's name and logo are trademarked, and the source license they use does not allow you to use that trademark. The result being that you can't distribute binaries of Firefox, whether modified or not, with the Firefox name and logo - not because of the copyright on the code, but because of the trademark on the name and logo.
Is it really a trademark violation if you haven't modified the binary at all? If I wrap a MacBook's casing around some different hardware and try to sell it as a MacBook, that's pretty shady, but if I have a stock MacBook, I wouldn't expect Apple to have a claim that I'm using their branding on a product that's not theirs.