Automattic/Co-Authors-Plus — pull request #242 by bcampeau (2014-12-17 21:15:12+00:00)
Title: Removing check for is_user_member_of_blog 

I've discussed this issue a few times, but this line of code really breaks the spirit of Co-Authors Plus. Guest authors don't have to be users, so why should they be required to be a member of the blog to have an author archive page? I also have legit use cases (i.e. NY Post sites) where this breaks their author pages.