... a continuum/Word World/canon/whatever you want to call it functions like World One, and the canon stories etc are basically records of history, so the events of canon are things that have already happened - fics and sporkings therefore are sort of like 'going back in time' to a certain place in the fic, so yes, everyone technically has free will but we know how events are going to unfold because we're in the position of people from the future, as it were.

Hope that helps! And just because that's how I see it doesn't necessarily mean that's how it is :)