Does anyone know what there business model could be here? Technically they could get access to all federated content, just as regular instances do. But legally they don't own that content nor do they know what country it origi ated in. This sounds like a legal nightmare to me. Would they even be allowed to process content in any form created by EU users under GDPR?
Copyleft should absolutely work. Not sure what we are currently doing, but nearly every toot or reply in the fediverse is copyrighted content. You must explicitly or implicitly give a license to every instance to use and redistribute that content. I could imagine a field in ActivityPub that declares the license, for example using Creative Commons licenses. If this license forbids commercial use, Meta can't use it. Also nobody else, such as journalists? Probably needs more thought on how a license should work. It is definitely a sharp sword!