It's still pure ASM. It's just that I prefer to use armips, a specialized assembler with a lot of unique features that make it far more useful for ROM hacking purposes than thumb.bat.
As far as porting to Ruby, you could try it. Find all the equivalent offsets for the things in labels.s, and for the .org directives in unhidden-power.asm.
Realistically, parts of the code itself would likely need to be rewritten as well, because it expects certain values to be in certain registers, and any minor change to the functions (made between RS and FRLG) could easily have changed what registers it uses to store which values. But you might get lucky.