Since no one without a law background is able to read these usual cryptic software licenses, we decided to write a simple, clear and comprehensible one for our extensions:
You may use the extension in exactly ONE live Magento installation. We do not care if you have one or hundreds of domains under this Magento installation. We do not care about any staging, testing or development installations. But if you want to use the extension in another live Magento installation, you must buy the extension again.
Our extensions are not encrypted at all, and you may edit and extend the code freely. However, you must not distribute, sell or lend our code or parts of our code.