set root=(hdx,msdosy)
loopback loop /fossapup64-9.5.iso
linux (loop)/vmlinuz ...
initrd (loop)/initrd.gz
Are they?
Yes, they are. The ISO has been booted into a working system.
So this is my input for newbies to pup. If there is already a grub from an already existing linux installation with grub, puppy ISO could be booted by addtng the usual grublines.
The same lines also work with a little modification to load the OS using the extracted files from the ISO on the HDD.