There are two questions here One is to bypassing the login page and the second is showing you portal as the default one.
If you deploy your application seperately as a WAR then you should be able to access your portal pages unless you force login.
If you need to login and go to you portal by default then you need to add a property named portal.defaultObjectName to the Portal Database and set the value as the name of your portal. So after logging in Jboss would redirect to your portal.
Hope it helps