From Hyperactive Software:
Zygodact provides an easy, automated way to add a complete registration serial key system to your Runtime Revolution standalone application or stack. With only a single line of code, Zygodact will check to see whether your application has been registered with a valid serial key. If not, it displays a dialog requesting a user ID and registration key. If your user cannot provide a valid registration, Zygodact gracefully shuts down your software, disallowing access. Zygodact does all the work for you. It generates any number of customer serial keys for your application, and handles every aspect of requesting and tracking a valid software registration on your user's computer. Each serial key is based on your user's name, or a user ID, or any other data you choose. Once registered, your software is tied to the user's computer, which means no one can copy your application to another machine without invalidating the registration. For developers who may be concerned about users sharing their registration keys, Zygodact also returns registration information to your scripts, for use with an online validation or tracking database.