I wouldn't mind having that included in the download. The checksum, if it hasn't been disabled, should prevent people from joining multiplayer games, unless everyone is using the same version. Everyone would have to agree to use the cheat enabled version to cheat in multiplayer, which is a valid thing for people to want to do.
I think it's a one byte change. The text processing code called a function in the special hand crafted assembly segment (it was named differently than the rest) of the executable that did the cheat processing. The first instruction of that function was changed to RET, basically gutting the function. I had a text file somewhere that detailed the byte changes for the various patches. Not sure where it went, but this change would be easy to undo without it. Both the original EXE and current EXE are in SVN, so it'd be easy enough to load up an old EXE and see what byte used to be at that address. The function in question had a labelled name in OllyDbg. I don't remember the exact name off the top of my head, but it was quite obvious. If the labels are sorted by address, and someone scanned down the list to the address of the segment with the different naming scheme, the function name would pop out pretty quick.
Just checked into this quickly. Adding details for reference, for whenever someone takes this up:
In the DSEG segment, there is a function CheckChatForCheatCode at address 0x58642A.
The original first byte was 0x55 which corresponds to the instruction PUSH EBP.