The official Darcula Look and Feel for programming environments by Konstantin Bulenkov.
Darcula is a Look-n-Feel for Java desktop application and a theme for code editors. This repository focused mainly on Java look-n-feel and contains ready to use library here https://github.com/bulenkov/Darcula/blob/master/build/darcula.jar
Darcula Look-n-Feel is licensed under Apache 2.0 license and can be used in commercial products free of charge. However, I strongly ask you to use original theme name "Darcula" in your product. Links to this project from your products or a simple mention are very welcome, but not necessary.
List of projects with Darcula theme:
Please send me your project to add here
Resources about how to create your own look and feel can be found at Oracle's official website: http://docs.oracle.com/javase/tutorial/uiswing/index.html