How can an approver not be a 'user' of the system?  Is that possible?

Question:  How can an approver not be a 'user' of the system?  Is that possible?

I'm not sure about your question, what are you referring with "not to be an user"? 

It could  be possible to send the form to someone only using the email address and you do not need to have this user added on any place, only on the condition on your form where will be specified that the form should be sent to this email address once it is submitted. 

But provide us more details about what are you referring to, we will be glad to assist you on what you are trying to achieve.