Well, I don't know if there is a more specific answer to your question than: Knoppix is based on debian testing and debian unstable. If your question is provoked by a kind of fear that you may ruin the system when installing "wrong" or "unstable" software, you should know that debian can handle the installation of different versions of software pieces. For instance you can download and install software X from the "stable" package AND software X from the "unstable" package. But as I said: to do this, you should read a little bit about apt-get. And please forgive me: I think this thread and all of your questions should be better placed in the General Support forum. There you may find more and more extensive help.