It’s good to be able to report that the upstream ZPU project – and also the toolchain – has officially moved from its previous home to github, so the source for the GCC port can now be found here:  https://github.com/zylin/zpugcc\

Better yet, this repo contains the various build fixes needed to compile this old version of GCC on a modern Linux system, so much of my previous “Setting up the toolchain” post is no longer relevant, and has been updated accordingly.