This can't be the original source code.
https://github.com/Piddewitt/Loderunner/blob/main/Lode%20Run...
Original source, I imagine, would be very tersely commented, if only to fit in memory / floppy, and would have very short variable and subroutine names, and lots of mess and commented-out lines from experiments.
This looks like a very lovingly done disassembly.