I developed an application that uses Java Webstart. It needs write access to the disk so it has to be signed, but it would only be used by a limited group of users so I don\
Another option is to have this "limited group of users" lower the security level for Java. In Windows, you go to the Control Panel->Java and then one of the tabs is for Security (sorry on my mac right now and it is not quite the same). I believe that if you push that security level lower to Medium, you can get away with the self-signed certificate.