The License key is for the theme and not for visual composer. As per license terms we can not provide a license key of another product. However, you can still update the Visual composer using simple tricks shared in this topic : Update Visual Composer
Visual composer is an external component built by WP Bakery. We have provided the documentation on how to use this plugin in the theme package. You can check the following for more details about this plugin : http://codecanyon.net/item/visual-composer-page-builder-for-wordpress/242431