I think what means is that instead of having the fork under your organization, you would make it available as a fork that is on an individual’s account (your account, for example) that is linked to a current Unreal Engine 4 account. In that case, only GitHub users who are currently members of the EpicGames GitHub organization will be able to view the fork. That would mean that they would have to have both an active Unreal Engine 4 account, as well as having it linked to their GitHub account before they could see your fork.