In the US, rasterized font representations are not copyrightable, in contrast to vector representations. Emoji are very clearly a font, and Apple uses a rasterized format, so using Apple color emoji is fine in the US.
That's a leap that's far from guaranteed by the cases summarized in your link. A court or the copyright office could just as easily say "just as the latest digital outline fonts have elements that can be protected as software, emoji have elements that can be protected as visual art."
http://en.m.wikipedia.org/wiki/Intellectual_property_protect...