They are both Special Effects creators for the Movie/TV Industry -- although, they are not in the right city for most movie production, they do work for commercials quite a bit. I think the more memorable one was the Mountain Dew 'robot' machine that shot cans at a guy. They actually do show that in one of the episodes, and later use the base of that machine to pull up the elevator in that one where they drop an elevator to test whether jumping at the end of a long elevator fall can save your life. Myth Busted.
Although they do mention the lady that survived a 55+ story fall, and they explain how that probably happened.
The way they get away with residuals is that it is a PPS versus Revshare issue. The smaller producers know that they'll only get a 3-5 year run on a reality home improvement show. You rarely see 'More than Human' which I believe was one of the ones where they had a residual agreement. Once a show gets that critical mass, the producers get a bit more leverage in requesting those residuals. Get too greedy and another producer will create a similar show.
Junkyard Wars asked for residuals, my understanding is that Discovery felt the show was done, so, they created Full Metal Challenge which was a one-season show. Ratings dropped considerably because they lost what made Junkyard Wars unique. Cathy Rogers was one smart PhD and still produces shows in England.
ABC, er, Disney, er, Discovery likes that pay-once, pay more than you would have to, but, have no further licensing issues.
No different than sponsors that choose to pay PPS versus Revshare. You do what is in your best interest.