I installed the application vault thinking I had it in my license and I did not and am now wondering how to uninstall it? Can someone please let me know how to do this?
You need to manually remove them with "rpm -e" on red-hat like systems or with "dpkg -r" on a debian/ubuntu. No automatic uninstallation is available.
The list of the applications can be taken from Plesk CP - Server - Application vault.