How can you communicate that to anyone who displays your OpenGraph images? I always assumed that an OpenGraph image was free to be used as a link to the page, but it turns out that this is a risky assumption.

I may be wrong, but I believe the distinction is between if I were to link to your post with one of your generated images which would get served as og:image and if I were to re-host your image to have it stand in as an "open-graph image" on my site linking to your post then what are the repercussions for me.