Built on Laravel
Built on the modular Laravel PHP framework means it's easy to add functionality or integrate with other systems
Laravel is the PHP Framework For Web Artisans.
Expressive, beautiful syntax
Laravel is a free, open-source PHP web framework. It is designed for people who value elegance, simplicity, and readability in their code. It is intended for the development of web applications following the model–view–controller (MVC) architectural pattern.
Some of the features of Laravel are a modular packaging system with a dedicated dependency manager, different ways for accessing relational databases, utilities that aid in application deployment and maintenance, and it's orientated toward syntactic sugar.
But enough of copying Wikipedia, just have a look.
The source code of Laravel is hosted on GitHub and licensed under the terms of MIT License. The same as BoomCMS.