The CMAT is a package that combines a shotgun bot and a program that analyzes your performance against the bot and reports statistics, including an overall "CMAT" rating.
The CMAT bot itself is not a port. It is doom2.exe with a dehacked patch and a custom wad, which provides the highly desirable 'doom2 feel' for Classic Doom2 enthusiasts. The evaluation program is based upon PRBoom.
The bot has 3500 hitpoints, and generally takes between 24 and 40 hits to kill, depending upon how well your shots hit. It does not move like another player, but as Doom2.exe-based bots go, it is very reasonable.
The statistics the evaluation program reports are:
Core CMAT: The overall evaluation of your match with the bot. The evaluation method takes a number of things into account, and is designed to accurately compare performances between the ratings of 0 to around 200. Players who consistantly rate above 200 are essentially out of range for this evaluation method.
Hits and misses
Aim accuracy: The percentage of how many of the shots you fired actually hit the bot.
Shot accuracy: Considering only the shots that hit the bot, what percentage of your Combat Shotgun's pellets actually hit the bot.
Real accuracy: Considering all of the pellets you fired during all shots, what percentage of your pellets actually hit the bot.
AHI (Average Hitpoint Infliction): How many hitpoints of damage, on average, you did with each shot.