Create a new text file in Notepad with this:
q3map2 -game ja -convert -format map testmap.bsp
q3map2 -game jk2 -convert -format map testmap.bsp
it's as easy as that. chuck this into a text file, edit the .bsp name to suit your needs and save it as decompile.bat
then put your new .bat file nito the q3map2 directory and drop your bsp into the same folder and voila, you decompiled a map.
Light entities and texture alignment can be lost in the process though. Same goes for misc_model entities I think.
Edited by Circa