They are most likely using some of Apple’s built in audio effects. These includes the iTunes equalizer and various effects used in games and voice processing. The Bongiovi DPS algorithm is custom C code and cannot be simply placed into the protected audio stream. The digital output is protected because there is a potential for stealing DRM protected media.
However, Bluetooth is supported by DPS because it is a lossy format. Just be sure you have the proper profile selected in the Bluetooth category in the settings screen.