There are at least two different ways to replace the controller in this keyboard.
The Stapelberg folder contains the docs and configuration for using the custom controller created by Michael Stapelberg.
The alvicstep folder contains docs and configuration for directly wiring a Teensy2++ to the existing controller board. This follows the pinouts described in https://github.com/alvicstep/tmk_keyboard, which is where the name comes from.
Both hardware solutions should work with the same keymaps