Non-refundable, but eligible for eCredit if you cancel flight. The miles will be converted to eCredit and not refunded back as miles (when you use miles for FCM upgrades, you are redeeming them at 1 CPM). Don't believe there is a way to just cancel the upgrade and not flight and get eCredit back (at least not by the rules). It's also not possible to only upgrade one person on a res (it's all or nothing).