Note that the jogl-demos.jar, which contains the GearsApplet class, does not need to be signed! JogAmp Community signs jogl-all.jar and gluegen-rt.jar, which contain the JOGL's supporting classes; this is the only Java code which needs to be signed in order to deploy applets using JOGL and is the only certificate the end user must accept.
Sadly, due to Oracle's Java Applet Plugin update 7u51, unsigned applets are no more allowed and hence the Applet sandbox is being taken away.