In SAS you have the possibility to call functions in external libraries via call module, modulen and modulec. So why not call the functions in jvm library directly? Nice idea, but to call these functions, a JNI (Java Native Interface) environment must exist which cannot be instantiated in SAS via call module. So no way to call it directly.
The solution is to use a proxy which handles the JNI environment and forwards all calls from SAS to Java.