Topic on Extension talk:GeoGebra

In case anyone is trying to use this as part of a template, you just have to add

// recursive parse in case we are inside a template
if($wgVersion >='1.16') {
	foreach($args as &$arg) {
		$arg = $parser->recursiveTagParse( $arg, $frame );
	}
}

just above

...
// retrieve URL of image file substituting GeoGebra applet if Java ist not installed
...

Ok. I added your code although I still have to learnread about recursiveTagParse().