September 10th, 2014, 16:28
My guess is that the .ori filetype suffix is short for "original," renamed by an auto-installer that placed replacements for the stock files. The likely scenario would be to script the renaming of the original files prior to inserting the replacements. Without renaming the originals, the replacements would simply overwrite the originals, causing them to be lost if the addon was ever removed - in which case, the user would have to dig into the install CD's in order to find the missing files (something this forum has seen many times).
That script could just as easily have used the .bak suffix, which might have made more sense to many users.