I tried to put as first line:
// include JavaScript
$this->API->addJSFragment("\n".' $GKMenu = { height:'.($this->API->get('menu_height','0') == 1 ? 'true' : 'false') .', width:'.($this->API->get('menu_width','0') == 1 ? 'true' : 'false') .', duration: '.($this->API->get('menu_duration', '500')).' };');
$this->API->addJS($this->API->URLtemplate() . '/js/modernizr.js');
$this->API->addJS($this->API->URLtemplate() . '/js/gk.scripts.js');
$this->API->addJS($this->API->URLtemplate() . '/js/gk.menu.js');
...but the plugin is loaded always first.
What is the line Mootools?