The purchase of publication rights is an equity transaction, in that a valuable piece of (intellectual) property is changing hands. And the law as written is murky enough that it's not simple to say that crowdfunding of public benefits wouldn't be covered. Not to say that Amazon couldn't be a bit more transparent about what their concerns are. By running a crowdfunding site under the new rules; is Amazon taking on unacceptable liabilities? Could Amazon be held liable by funders if unglue.it failed to secure rights to a book they had nominated to publish?

Those are serious questions that only a lawyer can answer.