I am not sure if thats allowed. I don't think the dispatcher will be able to find that forwarding addresses unless its apart of the same application or else anyone could access anyone elses servlets/jsps.
Each web app is going to need its own session, if they are running as seperate processes. If your using an application server, like JBoss you could consider using a session EJB, or if your not you could serialize the object and write it to file or database, and have the other web app read it from file, or database or whatever storage system your using. Again if your using an application server you could clone the session object and send it through the JMS to the second web app. Your going to need to synchronize the process. The way I would go is using a session EJB, unless you don't have a application server. Then store the session object somewhere and have the second web app read it from memory.