Developer / Publisher
Details and Conditions
From Valve's Video Policy:
"Use of our content in videos must be non-commercial. By that we mean you can't charge users to view or access your videos. You also can't sell or license your videos to others for a payment of any kind."
"You are free to monetize your videos via the YouTube partner program and similar programs on other video sharing sites."
See more details by clicking the "source" link below.
What it Means
Videos and streams ARE allowed
You CAN monetize on YouTube and Twitch with ads and subscriptions
You CANNOT sell or charge for access to your content (this would include Twitch "subscriber only" streams)
Any licensed IP or music not owned by the publisher are not covered by this policy