Done did. I traced the 6 pads on the back side to the Lattice CPLD. I read the datasheet for the CPLD, and measured carefully.
If we flip the PCB such as we see the 6 pads, and the GBA connector is downwards, the pins are as follows:
GND, TMS, TCK, TDI, TDO, VCC
These are indeed JTAG pins...