As far as I know, there is not a module available that does this.
To enable someone to register for an account, you will need to
A couple of things that might be handy: Community Commons module has a java action that will create a random strong password, also, if you add the Email Templates module and collect email addresses from registrants, you can email them a confirmation of their account registration. Also, if you want to know more about how anonymous users work in a Mendix app, docs.mendix.com has information regarding this. Note that starting in 7.1, native Mendix has username and password controls as well as a login button that can be used to create a custom login page.
Hope that helps,
Check the Appstore widget "Login form"