For example you will need two different license keys for test1.mydomain,com and www.mydomain.com.

The module will work fine if you are in TEST or SIMULATOR mode and you don't have a license key, it will just show a notice on the checkout page.

Once you buy the module we will send you the main license key and if you want development keys or additional keys you can email us. Development keys have no cost and additional keys do have cost but it varies depending on your setup, for example if you setup a new store on a previously licensed Magento installation its price x and if its a fresh installation its price y