The User Application Driver stores various kinds of information (such as workflow configuration and cluster information) that is application-specific. Therefore, a single instance of the User Application Driver should be not shared among multiple applications.
The User Application stores application-specific data to control and configure the application environment. This includes the JBoss Application Server cluster information and the workflow engine configuration. The only user applications that should share a single User Application Driver instance are those applications that are part of the same JBoss cluster. You should not configure a set of user applications to share a single driver unless they are part of the same JBoss cluster. Otherwise, your configuration could lead to ambiguity and misconfiguration for one or more of the components running inside the user application.