It's easy to fall prey to the idea that the ideal is that there is no authorities anywhere, but that's not the goal. The point is that you can choose your authority freely, and if enough people decide a given authority is no longer worthwhile, they can choose a new one freely.
Open source works the same way. Of course there are authorities for a given project who can choose what the final release is, but if they get too full of themselves or something it's easy enough to bypass them. It's happened quite frequently, so it's not an idle threat, either. You can't prevent authority from developing, that's wouldn't even be a good thing, but you can prevent it from abusing its current position of authority to lock in future authority.
Open source works the same way. Of course there are authorities for a given project who can choose what the final release is, but if they get too full of themselves or something it's easy enough to bypass them. It's happened quite frequently, so it's not an idle threat, either. You can't prevent authority from developing, that's wouldn't even be a good thing, but you can prevent it from abusing its current position of authority to lock in future authority.