The DJGPP project and its contributors were 100% volunteer. I'm sure some of the contributors took advantage of their involvement to obtain consulting gigs on the side (I did ;) but DJGPP itself didn't involve any. The Quake work was a swap; we helped them with optimizing, and they helped us with near pointers. Win-win!
Back then, DJGPP was a much bigger group, and most of the Quake kudos go to Charles Sandmann, author of cwsdpmi, who worked directly with Id to help them optimize their code for our environment.