HI this plugin looks almost great but I think there is a serious flaw in the latest version (3.0.5 ) as I installed it today and tried adding multiple authors. It would not allow me to add more than one of my existing authors but I was able to add my new co-authors - or guest authors.
I uninstalled it as I realized revamping my templates was going to take too long to finish today - but once I did that the meta box doesn't show up on posts anymore - I can't add new authors to new posts or remove old authors from old posts.
Is it possible my database was altered by this plugin and when I uninstalled the plugin some coauthor data was left behind?
You should also know I'm not using the default Post - only custom Posts Types for the install.
In the public part of the site I can still see the old author link is still visible and associated with it's custom post - however clicking on the author link no longer brings up a functioning author page i.e. /author/joeblow