If you want to replicate that project then you need the hardware the project uses.
Hardware
/bmw_bt_cdcemu_digital/ - KiCAD digital board. Contains the IBus transceiver, BT module and Atmega328p microcontroller
/bmw_bt_cdcemu_analog/ - KiCAD analog board. Contains the differential to single ended amplifier and power line filtering with power off functionality controlled by EN12 pin on the digital board