Chris Huelsbeck (Turrican, Star Wars Rogue Squadron composer) and I are streaming the unreleased GBC shooter Katakis 3D on Twitch today. Chris worked with co-creator Andreas Escher on the original Katakis as well as many other games back in the C64 era, so we managed to talk him into joining us and letting us play through the final build of Katakis 3D.
Katakis 3D has some pretty amazing graphics for a Game Boy Color title, and it is a shame it didn't see release. As for a public release of the ROM, well I am doing my best to get something done about that!
None of us are in contact with Manfred Trenz, so don't expect any updates on him.
We are broadcasting the game at http://www.twitch.tv/c_huelsbeck, starts at 3PM EST
You can read about Katakis 3D at Unseen 64