Also does the Tableau Software "user" take a license? Can this account be deleted?
All admin accounts must be an interactor so they will take a license. Any other account that ships may be set to unlicensed or deleted.
I wish this was improved and therefore suggested Improved server license model for medium size companies.
See also references to similar ideas in mentioned idea.
Ps. Some comfort: You can switch user rights on the fly and thus juggle between users who rarely use Tableau Server.