Magura doesnt have a dj specific fork. u could lower a freeride version possibly, but im not sure.
the atomlab is the gi60, 60mm of travel, not sure how good it is tho.
and your dj3 question. it may be possible, but it would be very soft, or your fork might explode, literally. the spring supports a lot of weight, adding the amount of PSI to get it to feel the same-ish would be emense. the fork wouldnt be designed for the pressure, you might blow the valve out. basically, dont even try it, something will die, maybe the fork...maybe you.
I ride on the Gi60 and i find it a great fork. you'll find it to be very stiff at first but after a few rides it loosens up. i use the stiff spring and its perfect, takes the jar out of big drop but you dont loose the speed on short run ins like you do with other forks. i have no idea on what the super stiff spring is like though.
one of the nicest forks i've ever ridden. kinda flexy, but it's amazing. i've had it over a year, never serviced it and it works perfect. i ride it almost every day to at the local DJs. so it gets used. its an amazing fork and wouldn't really want anything else.
i think white brothers in coming back into the game.
and there is a japanese company. i doint know the name. koos? woos? something like that. but they are supossed to be really nice. pinkbike did a review on them.