To disable the ZCM Login Screen in ZCM 10.2.x there was a good article from maggot62: Dynamically disable the ZCM login screen for users not in the User Source.
The developer made some changes in the registry for the new ZCM 10.3.x Adaptive Agent.
Here is the new registry key for ZCM 10.3.x.
In my case I even make one bundle to deploy this to all my servers where I need no authentication during a user source.
To disable it for both version of ZCM (10.2.x and 10.3.x) here are my registry files:
Editor's Note: With ZCM 10.3, all registry keys that were formerly HKEY_LOCAL_MACHINE\SOFTWARE\Novell\ZENworks are now HKEY_LOCAL_MACHINE\SOFTWARE\Novell\ZCM
Disclaimer: As with everything else at Cool Solutions, this content is definitely not supported by Novell (so don't even think of calling Support if you try something and it blows up).
It was contributed by a community member and is published "as is." It seems to have worked for at least one person, and might work for you. But please be sure to test, test, test before you do anything drastic with it.