If an application uses standalone non-web clients (application clients), and you want to use JSG, you must also set a system property for the client applications. A common way to do this is to add the property to the Java command line used to start the client application, for example:
java -Dcom.sun.CORBA.encoding.ORBEnableJavaSerialization=true -Dorg.omg.CORBA.ORBInitialHost=gollum -Dorg.omg.CORBA.ORBInitialPort=35309 MyClientProgram