Very interesting question, Anthere.
Is there even a generally accepted definition of '''free
content'''? A
search within the website of the Free Software Foundation yields no
results. No sources are cited in the article either.
Perhaps it is time for the Wikimedia Foundation (in collaboration with
Creative Commons and the FSF?) to create a free content definition, and
to make a list of free content licenses. In the meantime, it is hard to
see this article as being anything but shaky original research.
Erik