DW ReWrite creates a new ReWrite rule that will allow users to login and access the WP dashboard using "pretty" URLs instead of the regular,
Yes, This plugin is free to use and do whatever you want with it, use it on client website or your personal blog.
Yes, I know about this problem. I am working of fixing this. I am still trying to work out what is the source of this problem as this plugin works fine for 99% of people.