The original tutorial is marked as public domain, so I *think* that means that I can re-license this derivative work as I choose. IANAL.
I'm using the DCPU Toolchain (http://dcputoolcha.in/), with m4 for a preprocessor. The toolchain comes with a preprocessor of its own, but it just wasn't powerful enough to make assembly programming bearable for me. From the looks of things, I'll be contributing patches for the assembler as I fix various issues. It'll be a while before this Forth is ready to go.