That sounds awful. Thanks for posting about that, you just saved me from installing this plugin which would most certainly have resulted in a terrible user experience for our blog authors and a considerable waste of my time.
A plugin and its developer should be blacklisted for these kinds of things. The normal WP dashboard user experience should never be interfered with to such a degree that they can’t perform other necessary and basic WordPress functions or feel like they are being extorted when using a Plugin that has the option of using it for free. If they don’t want people only using the free version then they should not offer it.