Does this make it so that All Pages can only be edited by their author, or so that authors can choose to have their pages editable only by them? There is a difference, and the second option is what I'm looking for...
Topic on Extension talk:EditOwn
Sorry for the late reply. There's no choice for the authors, all pages are automatically restricted to being editable only by their creators and sysops. The author could, however, choose to put the page in a namespace to which the EditOwn restriction doesn't apply, see this.