UPDATE May 2014: Edgar Klüsener, the interviewer (who I haven't seen in over 20 years!) contacted me recently to say thanks for uploading this video; he had lost his copy years ago. He kindly gave me some more info on the interview:

"Just for your own info: the interview was primarily for a number of print publications, among those two guitar magazines (which explains some of the questions). The camera crew was hired by a German TV station who hadn't managed to secure their own interview slot and asked me if they could film my interview instead. Since I recorded the interview using my own device, I was not miked up, hence my voice was mostly captured by Kurt's microphone."

I recently found an old VHS tape with this full interview, and managed to get it onto DVD and now upload it. Way back in 1993, a friend of mine knew a guy who worked for German TV - he interviewed lots of bands. On a night out, I told him I was a big Nirvana fan, and he said he'd recently interviewed them, and did I want a copy of the tape! I said yes of course, and he sent me the tape. Here it is, I haven't seen this interview anywhere else, so I think it's pretty rare. Enjoy!

Update: Apparently the interview date was August 10, 1993 - Thanks to phineas117