ZF has been a supplier for BMW, Porsche and Jaguar over the years - long running supplier for BWM...
The major engineering is done by ZF, and there's tweaks to shift programming and gear ratios for each manufacturer to suit their specs (curb weight, max engine torque, final drive ratios) for the final package.
This is much like the way Tremec supplies various versions of the current TR-6060 that is/was used in Corvette, Viper, Mustang, Camaro and Challenger...same basic unit with some modifications for the application. (i.e. heat-treated components for extra durability in Viper apps...)
For those '11 SRT 392 buyers - those Getrag diffs get shot-peened internals for an extra measure to cope with the new 6.4 engine's higher torque output of 470 ft-lb (net, at crank)