Where is the link of latest updated article of this article?
and why apple archived and no longer updating it?
Well as it says in the article:
"Open Firmware is used in computers that use PowerPC processors."
and Apple stopped making PowerPCs as of 2006.
So the most recent of the iBooks could use up to Leopard, 10.5.X, which at this point is 5 OSs back.
Is it you can't open a legacy Open Firmware password?
Open Firmware password can't be opened - "legacy image should be converted"
Or need to convert a DMG: