The license key gives you access to product updates and email support from the EmPress team for questions related to their products. Your license key is free for the first year, and you will be notified at the end of the year if you'd like to renew your license key at a 20% discount for continued product updates and support. Your site will continue to work without the license key, you just won't be able to receive product updates and support from EmPress without an active license key.