Very intriguing question.
Steemit doesn't allow, or at least will send cheetah or steemcleaners, your way if possible copy/paste evident... and Amazon has copyright searches... so who owns what we post?

Never gave it much thought until now. I believe if you prove to Amazon that you are owner/publisher of original work then it could be published. But is it worth hassle? I know when you publish a free read on KDP they usually make you check box that you won't offer free on another site for 90 days.
I don't shop Amazon anymore... too political and I rather shop local small businesses now.