DPF is diesel particulate filter, however to complete a DPF delete you must remove the physical components and reprogram the truck's computer.
Usually this is recorded in the codes and will be detected by the dealer's engine code readers, thus voiding the factory warranty.
Also, as bully dog has the ability to re-tune the computers to run either more efficiently OR at a greater horsepower, sometimes this can cause damage to the engine. Even in the bully dog instructions, they warn you that as you increase the output you can damage components.
I have invested $40 on a new truck with a 100,000 mile warranty, I choose not to attempt to modify the exhaust, or add a bully dog that may increase the need for a warranty repair that I potentially could void just by having it on the truck.