Is licensing required for the users to approve Purchasing documents via an email?

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We have around 40 employees who will be setup as approvers for the Purchasing documents. We will be configuring Job level hierarchy.The intention is that the approvers will be approving the document via email notification.

Now the Customer is having limited number of licenses.
We have below queries to be addressed for approval configuration :-

Does the approver needs to have user account created to approve the purchasing documents?
Will this user accounts without any roles except Employee role will be treated as a separate licence?

Is it possible to the approvers without user account created to approve the purchasing documents via email?