What does the Stream license in O365 actually do?

Stream License allows you to control licensing at a user level but what a user can do depends on what kind of license they have. You can see details here https://stream.microsoft.com/en-us/documentation/stream-license-overview/ Also, Stream has an admin capability where you can restrict who can upload. - https://stream.microsoft.com/en-us/documentation/stream-restricting-uploaders/. Please let me know if I answered your question.