As per Fucadia's legalese, users who upload their own, original artwork and code to a Furcadia dream own the copyright to it. What exactly that copyright is isn't specified as far as I can see, but doesn't explicitly allow other Furcadia users to include it in their own dream.

That would imply they pay for thousands of copyrights, that's just not viable, perhaps they mean that they are protected under creative commons

You don't have to pay for copyright. Copyright is automatic.*

* in signatories of the Berne Convention

Wanna know my dream? I was playing garrysmod and Lorne laninng conected and crashed the server

(i'm not making this up.)