As of right now, only those with Workfront licenses will display as an “approver” on the Proof Approval report. In our department, we send proofs to external users for review and approval and as of right now there isn’t a way to track the proof approval process (decisions, last update, etc.) on those proofs that are sent to external users. Currently, there is only the email notification that our Workfront users get when a decision has been made.