There is no Ketron module inside... But VArranger comes with iots own softsynth, and sound expansions to mimmick, Yamaha, Ketron, Roland and Korg sounds... So he might be using those..
From Feedback on the Varranger forum, i know these soundsources are really accurate, so you dont require a Ketron soundsource anymore..
This is the buildvideo and i can not find any evidence of a Ketron module. Check after 56 secconds there is the full line up of the parts.
In regards to this DIY keyboard setup, Dan says on his Facebook, "Indeed, there is a Ketron SD1000 inside :)"
I understand Dan has four high quality sound banks. I don't think the 4 banks are geared towards emulating 4 different hardware modules per se but accommodating style formats. This is what Dan says on his vArranger forum, "We actually have 4 SOUNDBANKS (not SF2 format) that helps to give good compatibility with most of styles from the 4 styles brands KETRON KORG ROLAND YAMAHA They are approx 4GB in total"
If a person uses an arranger in every gig, I'd say even hiring a technician to make a custom vArrnager setup is worthwhile. I just like the fact that one can use any midi keyboard, midi controller, and wireless keyboard with vArranger. A couple of weeks ago, I received a Bluetooth foot pedal that can be used to change sounds and do many other functions with vArranger and other DAWs. It will be released sometime in September.