Based on an email I got from someone in Japan (not a composer), this is what I was told:
Via Ko Hayashi & Tadayo Aita,k.h.d.n. official spokeswoman (@gojarudegojaru) twitters, 'k.h.d.n.' will probably take a hiatus from their activities in its name for unknown period. i'm shocked! They announced Karous OST and their private (doujin) CD in Japan M3,but would cancel them
At the same time Klon Co.ltd,their company,will close its shooting game section.
I presume that is why all of those pages are no longer available.