Are the fortnite music dances copyright?
In addition to Moritz 'comment: The excerpts are also claimed on YouTube - that means - if you should be a YouTube partner, you will not be able to monetize the video.
That is why there's the function in the settings (of Fortnite) to mute such emotes in the game, because Twitch has recently been cracking down on copyrighted music.
So I can only recommend you the setting regarding the muting.
Nice day!