Hi,

the 3rd is by Danielsen, Explorer / Companion 2 code, working the table backwards.
Piece ordering K to p:
White even: 02 04 06 08 0A 0C
Black odd: 03 05 07 09 0B 0D
Orientation in ram 0080: A1-A8 -> 00B8: H1-H8
I always considered board representation and initial position construction very programmer specific.
Nice examples. For the other one's I would have to take more time, I'm a bit rusty with chess code at the moment.

Best,
Michael