Enterprise and MicroISV edition users have had the ability to automatically send out license codes to their end-users when they purchase a licensed product online. Today the server side license key generation components which are required for integrating with payment providers have been released as a separate upgrade. This means that Bootstrapper and Hobbyist edition users who sell their products through ClickBank, FastSpring, PayPal or other payment providers can now simplify their sales process by having the end-users license code sent directly by email when a purchase is completed.
A separate license code is required for the server side components, you will receive yours directly by email when you purchase it online.
2.1.6 Required for Bootstrapper & Hobbyist
The license key used for the server side components is not valid for use in the License Manager. Instead it will allow you to automatically send your clients an email whenever they complete a purchase, License Generation component from version 2.1.6 support the standalone IPN upgrade codes. If you purchase a MicroISV or Enterprise license you do not need to purchase this upgrade as it is already included in these editions.