Compared to the wealth of information and research that's available for popular machines like the CPC, ZX or C64 that's indeed not much :) But true, since Bomb Jack is only built from well-known standard parts, the schematics is all that's needed (although there are some minor problems in it, like missing or faulty labels).
hardware schematics, dumped rom, source of a working emulator... What do you want more ? :)