Quote Originally Posted by probono
I am not a legal expert, but if I were you, I would put my proprietary software on an USB stick so that it is completely separate from the Knoppix CD. This way, it would be obvious for everyone which part is Open Source (the CD) and which part is not (the stick).

If you have to combine everything on one CD, you should do as much as you can to not make it look like your software was "part of" or "integrated with" the rest. Remember, most law professionals are not IT professionals
This does not solve the problem if the propietary software uses packages like MySQL or QT. These companies require the software that uses them to be GPL or purchase a commercial license. Check their website for more info on their particular license practices. If the software uses packages like OpenSSL, it can only be distributed under GPL terms.

Check the GNU site for details on the GPL:
http://www.gnu.org/licenses/gpl.html
http://www.gnu.org/licenses/gpl-faq.html

I hope this helps