This add-on uses the concrete5 registration page, and packages it as a block.
It's just the form to fill in. It still get's posted to the core registration page.
When someone does not match passwords or does anything else that fails to register process, the user will be redirected towards the core registration page.
Very handy if you want to show a registration area, but not have the guest leave the page.
This the code is strongy inspired by the code used for the registration page. Were it not even partial copied.