This is a handy little OS 9 program that will un-merge a map file.
From the read-me:
Marathon Map Splitter takes a merged Marathon scenario file as produced by Forge and splits it into individual map, physics, and terminal text files for each level. It also extracts any resources into a "Terminal Picts" file. It is the exact opposite of the "Merge Levels" command in Forge. This lets you do things like peeking at other people's physics models (ever wondered how to make a potatoanus?), fixing the bugs in Blood Tides of Lh'owon, and converting old Pfhorte-generated scenarios.
These are some handy little applets that change the filetype of anything you drag onto them. They're useful for playing windows-based maps on a mac, or looking at them in forge. The tools are somewhat dated, as most recent maps, shapes, etc are in the universally compatible format, but the file typer may still be of some use.