@BoyC: it works!! I just made the following test: unpack MJM1 files (using dynamite), and add the "mjm0" header at start: game starts, and it is even faster to load (using DOSBox). The files are rather small too so no big deal.
Your version executable is the same as ours, data files are different. Maybe they lost the PKWare license at some point
@Kroah: Means that using the MJM0 header trick it is possible to edit IBM PC files and save them back for new levels.
I reckon that .TAD has a rather generic: handles poison, cure potion, to sum it up it seems to handle objects rather than rooms.
Which means that if you use the objects like in the original level it will work. If you don't use the objects it will work even better
I could've told you that MJM0 was uncompressed. Basically any x86 disassembler will disassemble the .TAD file. You can compare with the 68K version I started to resource some time ago.