There probably *are* people who own the
"copyright", but to be honest I
doubt you could persuade them to care. Furthermore, things like memory
expansions and the like are too generic to even attempt to copyright -
there's no way on earth you could assert any rights over a 74LS138 used
as an address decoder...
This reminds me of a 3rd party DIO memory oard in one of my HP9000/200
machines. It's something like 'Revision J'. After figuiring out the
circuitry, I discovered it's electronically the same as the HP RAM board,
but with some gates re-assigned (there might be a could of '00s on the
board, giving 8 NAND gates, exactlu whcih gate is used for which function
differs between the HP and 3rd party board). I heard a rumour that the
reason there were so many revisions is that they modified things until
either (a) the HP lawyers left them alone or (b) they felt HP would leave
them alone (I've heard both versions).
-tony