Freespire 3 does not boot

[probonopd]

When trying to boot freespire-3-x64.iso using SystemImageKit, getting

Running /scripts/casper-premount... done.
done.
/init: line 3: can't open /dev/sr0: No medium found
/init: line 3: can't open /dev/sr0: No medium found
/init: line 3: can't open /dev/sr0: No medium found
(...)

Possibly an upstream bug.

Additional information:
This is the GRUB entry generated by SystemImageKit:

menuentry "freespire-3-x64.iso - casper 1.376.2" --class ubuntu {
        iso_path="/boot/iso/freespire-3-x64.iso"
        search --no-floppy --file ${iso_path} --set
        live_args="for-casper --> iso-scan/filename=${iso_path} console-setup/layoutcode=de locale=en_US timezone=Europe/Berlin username=me hostname=host noprompt init=/isodevice/boot/customize/init max_loop=256"
        custom_args=""
        iso_args=" "
        loopback loop ${iso_path}
        linux (loop)/casper/vmlinuz file=/cdrom/preseed/custom.seed boot=casper iso-scan/filename=${iso_path} quiet splash -- ${live_args} ${custom_args} ${iso_args}
        initrd (loop)/casper/initrd.gz /boot/iso/additional-initramfs/initramfs
}

This is the system-provided boot/grub/loopback.cfg on the Live ISO:

menuentry "Try Freespire without installing" {
	set gfxpayload=keep
	linux	/casper/vmlinuz  file=/cdrom/preseed/custom.seed boot=casper iso-scan/filename=${iso_path} quiet splash --
	initrd	/casper/initrd.gz
(...)
}

[probonopd]

mkdir initrd-tmp
cd initrd-tmp
gzip -dc /mnt/casper/initrd.gz | cpio -id

grep -r sr0 .
# ./lib/udev/rules.d/60-cdrom_id.rules:KERNEL=="sr0", SYMLINK+="cdrom", OPTIONS+="link_priority=-100"

Looks similar to Ubuntu's. I don't know why it is looking for /dev/sr0 during boot.