If you want to check if all the packages you have installed on your Linux (Debian based) are free software you can use the vrms software to check it.
vrms is according to its site:
The vrms program will analyze the set of currently-installed packages on a Debian-based system, and report all of the packages from the non-free tree which are currently installed.
Installing and using it
sudo apt-get install vrms
The output on my PC was:
fglrx-control Control panel for the ATI graphics accelerators fglrx-driver Video driver for the ATI graphics accelerators fglrx-driver-dev Video driver for the ATI graphics accelerators (devel fglrx-kernel-2.6.18-3-686 ATI binary kernel module for Linux 2.6.18-3-686 fglrx-kernel-src Kernel module source for the ATI graphics accelerators fglrx-sources Source code for the ATI graphics accelerators control opera The Opera Web Browser skype Skype - Take a deep breath 8 non-free packages, 0.7% of 1127 installed packages.