It's a two line code change. This is ancient history ...
Look in the vicinity of line 485 of EDACS.cpp. Specifically, replace:
info.cmd = orf;
... with ...
info.cmd = orf ^ 0xA0;
newRaw ^= 0xA0;
For most folks, the worst part (due to lack of familiarity) is dealing with the quirks of Watcom to build a protected mode DOS program.