In the latest versions of the Ducky firmware it has been possible to simply change the VID&PID that tells the OS what the Manufacturer and Device type is.
This page allows you to generate a file that is placed on the sdcard alongside the inject.bin and will change how the OS registers the device
For example, Selecting Apple.Inc and Keyboard [ALPS] will make the ducky appear to the OS as a legitimate apple keyboard.
This list is updated regularly from http://www.linux-usb.org/usb.ids which maintains a list of USB IDS. It has not been filtered for only keyboards. If you would like to generate one and send it to me happy to update.
List Correct as at 2017.02.12