This engine is the code behind "The game Creator's" FPS Creator development tool, A powerful, yet rough FPS engine.
This is a very good engine for beginners and advanced users alike. I have been making games with this for a while, and it is one of the few "good" game creation softwares that i have stumbled upon. Also, anyone familiar with the Slenderman's Shadow series should know that this engine was used to create those maps, so you know that it's pretty damn powerful!