Sorry about the confusion. There are two slightly different versions, as the two sets of files in Github indicate:
I am pretty sure what you should be looking at is the os22_diy, not the os22_rev_diy. The difference between them is mainly that the former uses LM2596 regulator while the latter uses MC34063. The crystal for both versions should be 16MHz (the schematics say 12MHz, which is a mistake — 12MHz is what OS 2.1 uses). The voltage regulator on your PCB is MCP1700-33 (small, SOT-23 type).