oops, guess I didn't get to the post fast enough. I'd still be interested in creating a simple Hello World with comments anyways, system or not.

edit: on-topic, I made a .txt file explaining what I know about making LOGO_*.PRG files and put it in the freemlib repo:
https://raw.githubusercontent.com/freem/freemlib-neogeo/master/doc/LOGO_x_PRG.txt