Page of npm package is [1].
Although the license of the source code files appear to be MIT, the actual emojis are under a non-free license [2] that redirects to [3].

The following point of the license are enough to call it non-free:

4. Businesses can use our free emoji for testing purposes only.

[1] https://www.npmjs.com/package/emojione
[2] https://www.emojione.com/licenses/free
[3] https://www.joypixels.com/licenses/free