Once an app is ' purchased' by the Apple ID it is always part of the history for that account so cannot be removed from the VPP portal. You can delete an app out of AirWatch by clicking the little ' x' at the left of the app listing. It will remain gone until you click ' Sync Assets' for that OG. Then it will again list all the apps ever purchased and if the app is no longer in the app store it will be listed as ' Unknown.' They cannot be deleted manually. Those ' Unknown' apps can get to be a long list so support can help with a script on your database to delete all of them. I run that script when I want to clean it up now.