Use decensoring patch (Windows only). Back up the original Doom 3: BFG Edition's DOOM.WAD and DOOM2.WAD files. Download the and extract the bfgdecens folder to somewhere temporarily. Go to basewads, copy the DOOM.WAD and DOOM2.WAD, and paste them into the bfgdecens folder. Run doom1.bat and doom2.bat. These should generate two new.WAD files ( udoomcen.wad and doom2cen.wad).
Doom Split Screen Switch
Rename udoomcen.wad and doom2cen.wad to DOOM.WAD and DOOM2.WAD respectively. Put the newly uncensored DOOM.WAD and DOOM2.WAD files back into in basewads.