Actually, no. Xdebug is another great debugging application and not related to this project. The similar name has nothing to do with the other application, no matter what the people say.
xn - stands for Xell-Network
It is the name of the origin software package, where xn.debug was born from in 2005. The focus of Xdebug requires a server library to run and allows a very good IDE integration. xn.debug instead is build to work directly without server libraries and focuses on the on-demand debugging. Both tools have their advantages and could be used parallel if needed.