Forth OS are using the EFI Application of https://github.com/vathpela/gnu-efi

copy disk_nmt to USB boot flash

see also http://wiki.forth.org.ru/ForthOS http://fpauk.narod.ru/BochsSPF-OFW.tar.xz https://github.com/openbios/openbios

intermediate version http://fpauk.narod.ru/gnu-efi-code-forth.tar.xz