Developer / Publisher
Blue Isle Studios
Details and Conditions
From Blue Isle Studios' Contact Us page:
"For YouTubers inquiring about the possibility of recording and posting footage from our games,
we have no problem whether you are a YouTube Partner or not. Go ahead, you have our permission."
There are no explicit rules against streaming only for paid subscribers on Twitch. I would recommend contacting the developer for certain just in case as an extra precaution.