Emojis, just like any other form of art, are copyrightable and/or patentable. Take for example, the following emojis: 😍 🙌 💯 — while each are approved by Unicode, the specific design implemented by each operating system or browser may be copyrighted by the creator of the software. Unicode in turn releases the emoji under the following copyright:
Permission is hereby granted, free of charge, to any person obtaining
a copy of the Unicode data files and any associated documentation
(the "Data Files") or Unicode software and any associated documentation
(the "Software") to deal in the Data Files or Software
without restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, and/or sell copies of
the Data Files or Software, and to permit persons to whom the Data Files
or Software are furnished to do so, provided that either
(a) this copyright and permission notice appear with all copies
of the Data Files or Software, or
(b) this copyright and permission notice appear in associated
Documentation.
In other words, while using the unicode of an emoji is permissible, the rendering of the design of each unicode emoji by each operating system or software can be copyrightable by the owner of the software. Thus, the emojis shown above would probably be rendered differently based on the operating system or web browser you are using to read this post.
For example, if you like Android’s version of an emoji better than that of Apple iOS, and would like to use that specific design, you will need to request permission from Google’s legal department (to ensure there is no copyright or patent infringement) — even if the software itself is released under open source licenses.