The JAAS-based JRun 4 security architecture is incompatible with the proprietary JRun 3.x security architecture

http://livedocs.adobe.com/jrun/4/JRun_Service_Pack_1_Guide/4relnotes9.htm
http://livedocs.adobe.com/jrun/4/JRun_Service_Pack_1_Guide/4relnotes9.htm#1177288
To use a custom JRun 3.x security implementation class with JRun 4:
Confirm that your customized security implementation can be used in JRun 4 and modify as necessary, as described in "Usage notes".
Open the JRun server's SERVER-INF/jrun.xml file.
Comment out the JRunUserManager service.
Add the following JRunUserManager service, specifying the fully qualified class name of your customized JRun 3.x security implementation in the authenticationManager and authenticationInterface attributes:

true
authentication.ClassName

authentication.ClassName


Save the jrun.xml file.
Copy your customized security implementation to the jrun_root/servers/lib directory.