From what I have read about snakes in general, even mature males in breeding frenzy tend to not really harm eachother. The game of dominance between ball pythons seems to be more a contest of strength, who can push the other's head down to the ground more than which one can kill the other first. Though biting can occur, it is less a concern than say, two male mice fighting it out for dominance over a group of female mice.
However, when both males are out at the same time, it is good to keep an eye on them. They may completely ignore each other or try to dominate each other as described above. I know many breeders will put two males into the same cages to get them to combat each other and stimulate the breeding response, especially for males who seem a bit slow on the uptake when placed with a female.
Housing snakes together can be a problem more so than having them out in neutral territory. Large snakes with smaller snakes, especially with species of snakes that prey upon other snakes, is a great risk. Kingsnakes for example will easily eat a smaller snake of any species. Even non snake eating snakes can accidently eat cage mates or snakes they are around, should they smell prey on the other snake.
Housing snakes of different species in the same room, each in their own individual cages, shouldn't cause any problems at all. I have Brazilian rainbow boas, corn snakes, ball pythons and a texas rat snake all kept in the same room, without any problems. (all in separate cages of course). As for having them out at the same time, I never tried. Keeping track of more than one snake out at a time is enough for me. Even then I have to make sure they don't decide to go hide in the back of my couch or head in some direction I don't want them to go.
I can see two snakes out at one time will decide to go in opposite directions, which makes it a bit easier one may get out of hand and risk escaping.
