I used the trial version JBuilder 2008 on jre 1.5.0.12 with Geronimo 2.1 and with the default WTP inside JBuilder 2008, it could setup the server. But when I deployed the working ear to the server, it complained that there is no deployer to handle it. But the ear can deploy to the standalone Geronimo 2.1. Even for the WAR, it can too.