It is a popular method of php-files encryption. It is free and you can download it directly from the official website.
Almost all code of JBZoo is open except the parts where the license is checked. Starting from version 2.0.0, IonCube Loader module support is required for the proper work of JBZoo.
ionCube and a hosting
Almost all hosting providers support ionCube module. If not, you can ask your hosting tech support to enable it and in most cases it will be done on your first request.
Installing ionCube on your own
You can add the module support for your server yourself (if you have required permissions). In this case installation wizard may help you (you can download it from the official website).