To uninstall context-nonfree just follow these instructions.
/parrot/jollyroger/non-free///install/index.html Non-free items from the ConTeXt distribution not considered free from Debian perspective, which are included here. Parrot 3.7 non-free/tex 2007.03.22-1
sudo apt-get remove context-nonfree
Which will remove just the context-nonfree package itself.
sudo apt-get remove --auto-remove context-nonfree
This will remove the context-nonfree package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for context-nonfree then this will work.
sudo apt-get purge context-nonfree
Or similarly, like this context-nonfree
sudo apt-get purge --auto-remove context-nonfree
|Maintainer||Debian TeX maintainers
|Description||Non-free items from the ConTeXt distribution not considered free from Debian perspective, which are included here.|