Eclipse starts JBoss by directly running the main class, org.jboss.modules.Main
in jboss-modules.jar
.
Open the server configuration (doubleclick on the server in the 'servers' view).
There, click 'Open launch configuration'. In the dialog 'Edit Configuration' open the 'Main' tab. There you see the option for the main class, which is 'org.jboss.modules.Main' by default.