This plugin is an add-on that requires the Bookly PRO installed and activated. View Bookly PRO page at Codecanyon. This add-on enables Bookly to become a Multisite ready plugin. After installation and activation of this add-on you can use Bookly in your Multisite environment. Please note: As it was clarified here by Envato staff you need to buy an additional Regular License for Bookly plugin and every installed add-on for each additional domain name that you use.