Since 99.99% of us here are not Knoppix developers, we can not get povray or povray GUIs on future releases without someone filling a bug report. http://www.knoppix.net/wiki/Bugs/4.0

So the best I can do is to suggest that you install povray. I go to http://packages.debian.org and search for povray under ANY and I discover that it is in the Debian package management system. So to install povray on Knoppix 3.8.x and Knoppix 4.0 (3.9 is buggy; Do not install apps on 3.9), assuming the network is properly configured & the machine can access the internet, is as simple running two commands:
Code:
sudo apt-get update
sudo apt-get install povray-3.5
The first commands refreshes the lastest package info from the package servers. Then second command tells the system to install povray. It will download, decompress, and setup it up for you. The total download size start to finish is about 11MB.

If this is too much command line mumbo-jumbo, then I agree. That is why GUI tools were made to allow easy access to the package management system. Run the program synaptic or kpackage. Refresh the packages lists (effectivly a 'apti-get update'). Do a FIND or CTRL-F. Type povray. It will find the package. Click apply and it will download, decompress, and set it up for you.