Yes its rare hardware and if someone was daring enough and looked into it you could get any card cloned. There are cloning services out there and "ic break". With just a small run of 400 cards you could easily change things.
http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=pcba+cloning
Which one? The A600 or the Vampire?
I'm guessing the A600 is simple enough with all the expired patents that it wouldn't take much to clone.
The Vampire? It's all in the firmware of the FPGA. A clone wouldn't be nearly as useful as a re-creation using an ASIC in place of the FPGA anyway: Something that's already being planned by the Apollo team with the code to do it with anyway.
-edit-
Oh, the Blizzard PPC. It's not much of a performer among PPC boards. If you want to run OS 4 there are cheaper ways to do it. Frankly, the clone would cost as much as a new machine anyway. It's a kludgey design to start with. The 68060 or 68040 for the backward compatibility would make the whole thing too expensive to use! You'd need an FPGA to make the 68k side cost effective and with the Vampire around, you can make a 68k that can run faster than a PPC can emulate anyway!
