Add-on Email optional in the registration [paid]

[rafass]

Ideally I want 'email address' to be an optional field if a certain option is selected (a custom user field, radio buttons). For example, if I had a question 'subscribe to newsletter' and they pressed the 'yes' radio button, the email address field would become a required field. If they pressed 'no' the email address field would be optional (and they could complete registration without filling that box in)

I really would like to make more simple the registration process. and I would like to make optional the email address. something like this would be really cool:

Anyone interested? I'm accepting PC's