This references the latest version of Geogebra available at http://www.geogebra.org/. Unfortunately this cannot be used in WeBWorK questions that interact with geogebra. The security rules for the javaScript communication require that the java applet (geogebra) and the calling page (the WeBWorK question) come from the same domain. (You can check the version number under the "Help" menu in the geogebra window.)
This references the version of Geogebra available on thei WeBWorK website. (You can check the version number under the "Help" menu in the geogebra window.) This is the version of Geogebra referenced from within most webwork questions.
Sources for the applets used in WeBWork demos: README