The CD was produced for distribution with the German Linux Magazin, so the default language is German.
You can change the language to English, though.
To get a English KDE desktop, specify "knoppix lang=en" at the boot prompt, then boot.

If Mozilla comes up and you see the OGo login screen, do: Log in as a user, then at the upper/right you'll find a link labeled "Praef".
Click it - you are taken to the main preferences panel, select the link "Anzeige" (display).
At the very top of the display preferences there should be a popup where you can select English as your language.
Press save, logout and login again. Voila, here you go