I was browsing the 4wd.com website when I saw that they now have ProComp front and rear driveshafts available for JK's with 0-4" lift. And from looking at the pictures, it seems they are not a double cardan style like other shafts are.
Non-CV Style Front Drive Shaft by Pro Comp and Other Jeep Parts and Jeep Accessories by 4 Wheel Drive Hardware-RH1
This is from their website: The factory driveshaft ball and cage design joint is replaced with #1310 style u-joints to allow for a stronger engagement, increase the range of motion, and improve seal and driveline life. Exclusive yokes, not flange adapters, are used to allow for a longer driveshaft, unlike our competitors versions. Pro Comp Suspension rear driveshaft’s are constructed from 3.00”x 0.095” DOM (drawn-over-mandrel) steel. Kits come complete with necessary mounting hardware.
Now I know ProComp isn't the most popular brand out their, but it seems that a single cardan is safer for the drivetrain then a double cardan?