What causes ClassNotFound weblogic.iiop.PortableRemoteObjectDelegateImpl in JBoss EAP?

Issue

• In JBoss EAP 6.4, we have created a custom module containing the Weblogic wlclient.jar and using PortableRemoteObject.narrow to cast our EJB 2 remote home object to invoke an EJB in EAP 6.4, but are getting this error:

ERROR [org.jboss.as.ejb3.invocation] (EJB default - 2) JBAS014134: EJB Invocation failed on component Invoker for method public abstract java.lang.String org.jboss.playground.Invoker.invokeHello(java.lang.String): javax.ejb.EJBException: JBAS014580: Unexpected Error
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleExceptionInOurTx(CMTTxInterceptor.java:188) [jboss-as-ejb3-7.5.20.Final-redhat-1.jar:7.5.20.Final-redhat-1]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:281) [jboss-as-ejb3-7.5.20.Final-redhat-1.jar:7.5.20.Final-redhat-1]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:331) [jboss-as-ejb3-7.5.20.Final-redhat-1.jar:7.5.20.Final-redhat-1]
...
Caused by: java.lang.ExceptionInInitializerError
    at org.jboss.playground.InvokerBean.getEjbJBoss(InvokerBean.java:94) [playground-ejb2-ejb.jar:]
    at org.jboss.playground.InvokerBean.invokeHello(InvokerBean.java:48) [playground-ejb2-ejb.jar:]
...
Caused by: org.omg.CORBA.INITIALIZE: Cannot instantiate weblogic.iiop.PortableRemoteObjectDelegateImpl
    at javax.rmi.PortableRemoteObject.createDelegateIfSpecified(PortableRemoteObject.java:213) [jboss-rmi-api_1.0_spec-1.0.4.Final-redhat-3.jar:1.0.4.Final-redhat-3]
    at javax.rmi.PortableRemoteObject.<clinit>(PortableRemoteObject.java:67) [jboss-rmi-api_1.0_spec-1.0.4.Final-redhat-3.jar:1.0.4.Final-redhat-3]
    ... 62 more
Caused by: java.lang.ClassNotFoundException: weblogic.iiop.PortableRemoteObjectDelegateImpl from [Module "deployment.playground-ejb2.ear.playground-ejb2-ejb.jar:main" from Service Module Loader] (no security manager: RMI class loader disabled)
    at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:396) [rt.jar:1.8.0_161]
    at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:186) [rt.jar:1.8.0_161]
    at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:637) [rt.jar:1.8.0_161]
    at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:219) [rt.jar:1.8.0_161]
    at javax.rmi.PortableRemoteObject.loadDelegateClass(PortableRemoteObject.java:238) [jboss-rmi-api_1.0_spec-1.0.4.Final-redhat-3.jar:1.0.4.Final-redhat-3]
    at javax.rmi.PortableRemoteObject.createDelegateIfSpecified(PortableRemoteObject.java:209) [jboss-rmi-api_1.0_spec-1.0.4.Final-redhat-3.jar:1.0.4.Final-redhat-3]
    ... 63 more

• In EAP 5.0.1 :

1. We have multiple EARs deployed onto a cluster within the "farm" directory.
2. We have "isolated" set to true in ear-deployer-jboss-beans.xml
3. One of the applications uses and packages a modified 3rd-party library called "wlclient.jar", which appears in the VFS tmp directory as follows once deployed:
   1. /opt/jboss/server/<instance>/tmp/vfs-nested.tmp/a8cf58e_wlclient.jar
4. Another application, when running, will apparently (sometimes)attempt to use classes from this jar.  See error below.

        Caused by: org.omg.CORBA.INITIALIZE: Cannot instantiate weblogic.iiop.PortableRemoteObjectDelegateImpl  vmcid: 0x0  minor code: 0  completed: No
                at javax.rmi.PortableRemoteObject.createDelegateIfSpecified(PortableRemoteObject.java:184)
                at javax.rmi.PortableRemoteObject.<clinit>(PortableRemoteObject.java:61)
                ... 41 more
        Caused by: java.lang.ClassNotFoundException: weblogic.iiop.PortableRemoteObjectDelegateImpl (no security manager: RMI class loader disabled)