Details and Conditions
Doube Fine used to have an FAQ on their website with a very clear approval of YouTube monetization and no explicit rules against Subscriber Streams on Twitch. The developer has since been acquired by Xbox Game Studios and the website is now a one page placeholder. As such, the conditions now fall under Microsoft's policy which approves of YouTube monetization (with conditions), but not Subscriber Streams on Twitch. See the "Xbox Game Studios" section for more.