The more conversations I have, the more convinced I am that if larger actors in the fediverse wish to move from an implicit licensing to an explicit one; the only sound strategy is for all accounts to communicate licenses on a per-note/activity basis.
It would sidestep many (but not all) annoying legal questions like "if you author a public post, and send it to a remote server, are you considered a "user" on that server for the purposes of licensing of public posts for wider distribution"