After removing DeviceLock Agent from computers manually or with the 'Uninstall service' plug-in of DeviceLock Enterprise Manager console, the Group Policy Object with DeviceLock installation package does not install DeviceLock Agent on those computers. Event Log however contains the following message: Description:"The assignment of application DeviceLock Service from policy XXXXX succeeded."
This is expected behaviour in terms of the Windows Installer service and Group Policy processing: after a GPO installs DeviceLock or any other application on a computer, this specific GPO is assigned with "Applied" status for this computer on domain controller. When DeviceLock Agent (or any other application) is removed without using the same GPO it has been installed from, this GPO will still remain on domain controller with "Applied" record, thus it will not be processed second time considering DeviceLock is still being installed on the system.
To re-install DeviceLock on computers via Group Policy, you can:
a) Create a new GPO with DeviceLock installation package
b) Re-deploy application in the existing GPO (see 'Installation via Group Policy' -> 'Redeploy a Package' section of User Manual).