Første svaret jeg fant på google... Godt sted å lese er faktisk på Twitch sine hjemme sider.

"You can stream any music that you want, as long as you own a copyright for it. We do not check into user copyrights ourselves, as we operate under DCMA safe harbor laws, which means we have to be contacted by a copyright owner in order to initiate the DCMA process. For legal information see your terms of service and http://www.twitch.tv/user/legal?page=dmca "