FWIW I was able to compile it on RISC-V hardware (the SiFive Unleashed) running recent Fedora.

  $ make
  gcc -I /usr/include -I. -g -nostdlib -static -o jonesforth jonesforth.S
  $ gcc --version
  gcc (GCC) 10.0.1 20200121 (Red Hat 10.0.1-0.4)
  $ as --version
  GNU assembler version 2.34-2.fc32

The tests don't all pass, but the basic system seems to work.