To further clarify:
An "original" DMS is a DMS made by Phatnoise (in some cases rebranded, e.g. Kenwood), which has not been hacked or upgraded by the user to work in a hacked Phatbox/Music Keg. Since your VW Phatbox has presumably not been hacked, you need an original DMS for it to function. You also need an original DMS in order to hack the Phatbox to work with non-original drives.
If you do not intend to hack the Phatbox (you should do it eventually), and just want to get things up and running, you still need to use VorTechS' Windows DMS Hack Tools to load the VW firmware onto the Kenwood DMS. You will want to check the option to install the non-hacked firmware. You may also want to reflash the Phatbox with the VW firmware, in case it is not updated with the latest firmware (though it probably is). This option is also in the Hack Tools and is self-explanatory, though you will want to refer to the Phatbox manual for the firmware upgrade procedure.