It's the source code for MacenWolf, kindly made available by Nexion.
Straight from Nexion:
"On today's menu we got a full plate of source code salad.
There are some ideas if someone has the spare time. Ideas like better file handling, aspect ratio options or moving it to SDL2. Since MacenWolf is based on Wolf4SDL 1.7 you can port it to any other system Wolf4SDL runs on or like any that has SDL. The makefile for linux should work out of the box, in theory at least. The Dreamcast build should run fine with a few changes for the files but the audio file handling might need a bit more work.
I would be delighted to see ports for the C64, NES and AMIGA 500 in the next 7 days or else i will quit and delete all. Just kidding. Have fun and keep the mods and modding alive."
There's a bit more documentation in the readme files inside, go read those.
