AFAIK apple was quick to adopt Unicode7.0 and 8.0 first and released the new emojis with their own design of the unicode characters. Unicode is in public domain. They(emojis) must first be approved by unicode consortium, but the vendors may choose the change the designs. Since the unicode translation is same for everyone All android was to do was design its own version of same unicode as emoji since unicode(version) already has the support.
Update: No, licencing is not required since Unicode is open and public.