I noticed, however, that the form adds the new contact to the list directly, without having the person confirm by email. I think most people are used to this extra security step, making them feel reassured and in control of their subscriptions.
Any idea then on how to add that step to this great form? So that before the contact is added to the list, the person must first click a link received via email ?
What you would want to do is create the code on your server so that way when they submit it would send an email to them. Then once the email is sent you can have it sent a link with a custom link. That new link would go to the page where you would re enter the email and add whatever contact information you desire.