Is jThinRich just a wrapper for JNLP or WebStart?
No! WebStart/JNLP is just one enabler. By itself WebStart is just a wrapper for JNLP and for creating a sandbox by which Java applications can run on the desktop. What is missing is an application framework to allow developers to build secure and robust applications using a Java software distribution model while leveraging web services to communicate with a centrally hosted system. jThinRich applications are tightly coupled to the server for session management, persistence, rights and access control, and for some if not all their business logic. The client side is primarily for rendering what is stored and managed on the server and for providing the user with a rich application experience. If all you want to do is build a word processor or email client that resides on the desktop then for the most part all you need is webstart and good GUI components. There are several products out (some based on JNLP) that help you manage software distribution on your local intranet and tracking patch
