Sure there is. It hasn't been worked on much precisely because Apple wouldn't allow it anyway, but Ted Mielczarek ported Firefox to iOS a while back. See https://bugzilla.mozilla.org/show_bug.cgi?id=676585 and https://bugzilla.mozilla.org/show_bug.cgi?id=680878 and https://bugzilla.mozilla.org/show_bug.cgi?id=681602 and so forth.
Sure there is. It hasn't been worked on much precisely because Apple wouldn't allow it anyway, but Ted Mielczarek ported Firefox to iOS a while back. See https://bugzilla.mozilla.org/show_bug.cgi?id=676585 and https://bugzilla.mozilla.org/show_bug.cgi?id=680878 and https://bugzilla.mozilla.org/show_bug.cgi?id=681602 and so forth.