Core files that are a base implementation of cocos2d api. It is supposed to be used as a part of any cocos2d project. The implementation is similar to Controller.cpp that is the part of cocos2d engine.
This is a C++ library for Linux and Windows based operating systems that allows accessing the Steam Wireless Controller as a gamepad in the same way like a common gamepad.
There is no requirement for Steam SDK libraries.
However, it is likely that this project will be extended to support Steam SDK as well.
Please look at the demo how it works: Cocos2D Demo