The JC65 PCB actually has two revisions: A QMK native version, and a PS2AVRGB version. Jchan offered both PCBs as options during the M65-A Round 1 group buy, and were also available choices for the 65% acrylic case group buy.
These docs are for the QMK version of the PCB. More info on qmk.fm
Make example for this keyboard (after setting up your build environment):
Or to make and flash: