Must say this plugin is really simple... and quite unuseful as it's made.
What this plugin does is usually meant to be a repetitive and fixed task, and it's quite boring placing the schortcode at the bottom of EVERY post.
And, called in a theme it just outputs the "admin"'s last posts; who runs or writes with a such name user (security issues, ugly name...)?
In addiction, i run a multiuser blog, so it was realy uneuseful.
BUT, with just one basic edit it becomes useful:
author' => admin to
author' => get_the_author() it works as it's meant to do! ;)