In 4.03+, by default, .war module classloaders attempt to load classes before delegating to the parent classloader, except when using Application--J2EE visibility. With Application--J2EE visibility, .war module classloaders delegate to the parent classloader before attempting to load classes. You can change this behavior by setting the com.ibm.ws.classloader.warDelegationMode JVM system property.
For full details, see the 4.04 release notes on classloaders.