Alexandre Oliva wrote:
I get the impression you misunderstood the question. I'm not asking
something you could do if you had some other permissive license that
you couldn't do with the GPL. What I'm asking is whether you know of
anything that, in the absence of a copyright license, you could do
with a work, that, after accepting the GPL, you could no longer do.
In the case I described, there was a more permissive license on an
earlier work (pdtar), so the only relevant comparison is regarding the
difference before and after the GPL was applied with the modifications
that made it GNUtar, but if you insist we can pretend otherwise.
Let's assume that I have obtained my copy of several components under
any license but the GPL, and so have a lot of other people. In the
actual case they were free and redistributable, but the terms aren't
anyone else's business. With any other license, I could at least have
done a diff against the original copies and my work and given that away
(perhaps using line number references if the other work's license was so
strict as to prohibit the copying involved in context diffs), letting
others duplicate the results with their own copies of the components
(well, assuming they had a compiler for DOS too - I really thought it
would have been more helpful to give binaries away). The FSF says you
can't do that if any of the parts are GPL'd and the resulting work as a
whole can't be. This doesn't happen with any license but the GPL.
This would be a prohibition of the GPL.
Yes, in case it wasn't clear before, the specific prohibition that I
consider unethical is that it takes away my choice to share my own work.