Where does it cache the scripts that are added with the "@require" keyword? I'd like to know where it is on Mac OS X, preferably, but if you know where it is on another system then it shouldn't be hard to find on a Mac.
GM stores all of a scripts data within it's own folder within the
gm_scripts folder residing in your Firefox profile folder. To find your profile folder please read this page.
So to find the
@require'd files for script
xyz look in:
That's no longer true with recent Firefox - check this answer which tells that they are hidden away in a sqlite database.