I initially confused the 8501 with the 8051 which is a totally different architecture. However, a quick Wikipedia trip taught me that the 8501 is a later varian

I initially confused the 8501 with the 8051 which is a totally different architecture. However, a quick Wikipedia trip taught me that the 8501 is a later variant of the 6510 so they're pretty much compatible. Still very impressive of course, especiall the part of re-writing the kernel to fit the different pin-out.