Hi.... Well, we'd always planned to put the content online in an open format and to involve the community in building it out. You provided the reminder and impetus for putting it up on GitHub!
As of right now, there's no automatic/technical process for updating the Discourse forum directly. It will have to be a manual one.
We see two ways of moving forward... 1. we will keep the "official" master curriculum up on GitHub and manually port it when there are significant updates to Discourse. 2. If PWYM community members begin to make significant improvements, changes, additions, then we'll upgrade their status to author and they can make updates directly in the site. For now, it will be a manual process of keeping GitHub and PWYM in sync.