Requires 'memdisk' from /usr/lib/syslinux
I got my freedos.img file from the Clonezilla LiveCD...

<code>
label FreeDOS
        MENU LABEL ^FreeDOS
        KERNEL memdisk
        APPEND initrd=live/freedos.img
        TEXT HELP
Run FreeDOS
        ENDTEXT
</code>

Useful extensions on this: add support for USB storage class to the FreeDOS environment.
This will allow FreeDOS PXE boot to be used for BIOS flashing et.al.