The mmenu.js plugin is free to use for personal or non-profit usage. You can purchase a license if you want to use it in a commercial project (including plugins, themes and templates you plan to sell).
Before purchasing a license, please make sure the mmenu.js plugin is suitable for your project. You can do this by downloading the free version and purchasing a license later on.
By purchasing ONE "Multiple websites license", you are allowed to include the mmenu.js plugin in ONE product (for example a plugin, theme or template) for sale. Customers and users of your product do not need to purchase their own license.