Open games with closed content

“Some Linux users have at least a general familiarity familiar
with RMS’s four freedoms and the GPL. Some of the games mentioned
in this column, in the past as well as in the future, are licensed
such that the game itself is under the GPL or a similarly free
license, but the content is not. That is, you are free to do
whatever you want with the game engine itself, but don’t mess with
the content.

“For example, let us consider the game Sauerbraten. Now, the
Cube2 engine that is the heart and soul of Sauerbraten is totally
copylefted. You can distribute it, modify it, and even rub it in
your belly, if you so desire. However, the data files that are
associated with Sauerbraten is not free.”

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