The pricing model for XUI is very simple. Buying a license gets you the full source code and 12 months of updates, new features and bug fixes as well as troubleshooting support. After 12 months, there is no obligation to pay any more money and you can continue to use the current version of XUI for as long as you like. However, access to updates, support and bug fixes will stop.
A license grants either one developer (for the personal license) or all developers of an organisation (professional license) permission to use and modify the XUI source in personal and commercial applications. The license expressly forbids sharing of any of the XUI source code with other parties who do not own a license. This means you cannot publish open source projects containing XUI source code. You also may not sell derivative works of XUI (essentially you can’t just resell XUI or code containing the XUI framework as your own).