Q: Specifying licence on open-graph images? I am building a webpage with open graph tags to make an open-graph object.
When I set the og:image tag, is there any way to specify its license?
How other webapps fetching my open-graph object will be aware of its license?
Or these images are thumbnails and considered as public domain and reusable anywhere? 
Reciprocally, when I fetch some open-graph objects, can I display images defined in their og:image tag on my website?
I have not found the answer on the protocol website http://ogp.me
