If you use Debian or Debian based like Ubuntu, you can check if you have installed non-free software via Debian way. By Default Debian does not install it unless you put non-free on your apt repo, so delete it first if it exists.
Install the tool vrms (virtual Richard M. Stallman)
# apt-get install vrms
# aptitude install vrms
Then, delete all non-free software, mandatory if you want to be a 100% Free Software guy, also to make happy RMS :)
# apt-get remove –purge `vrms -s | xargs echo -n && echo`
# aptitude purge `vrms -s | xargs echo -n && echo`