UIkit is a lightweight and modular front-end framework for developing fast and powerful web interfaces. It comes with a wide range of reusable and combinable components. All UIkit classes are namespaced, so they won't interfere with other frameworks and extensions you might be using. Here's an overview of the different UIkit components, which you can easily modify using the customizer.
The Warp framework provides a rich toolset for developing cross-platform themes, including support for LESS, a Customizer and its very own front-end framework UIkit.
A lightweight and modular front-end framework for developing fast and powerful web interfaces. It is open source and MIT licensed and you are free to use without any limitations.