Xavi:
> What I still have not understood is:
> The copyright holder is legally empowered to exclude all others from
> copying, distributing, and making derivative works. [...]
> The license does not require anyone to accept it in order to
> acquire, install, use, inspect, or even experimentally modify GPL'd
> software.[...] we don't even want to cover those activities by
> license. Almost everyone who uses GPL'd software from day to day
> needs no license, and accepts none. The GPL only obliges you if you
> distribute software made from GPL'd code, and only needs to be
> accepted when redistribution occurs.And because no one can ever
> redistribute without a license, we can safely presume that anyone
> redistributing GPL'd software intended to accept the GPL.
> I thought that if you modified code, even keeping it to yourself,
> you needed a license from the copyright holder.
Think of books. You can do whatever you want with your copy of the
book. And it's legal, as long as you don't distribute it.
Obviously software is different, but the law is not. The difference is
in that the common user often doesn't get receive a modifiable copy.
Besides the technical problems in modifying object code, it's not a
trvial difference at all. With computer programs, you do *not*
receive a copy of the work. When a written text falls in the public
domain (ignoring the fact that things has been modified to move that
time infinitely far in the future) you can copy it as long as you want
(that's public domain, actually). But you can't do the same with
computer programs, since you won't have systems where they run, and
you can't port them to newer systems.
Plesae note that modification is not allowed (as far as I know) even
for public domain material. This because of "moral rights", but
porting is not effectively a modification (for example, you can
translate a public domain text, even according to "droit d'auteur"
legal systems).
> Isn't that making a derivative work?. Or copyright does not cover
> unpublished derivative works?.
No, it doesn't cover unpublished stuff.
> The GPL allows you to do private modifications, but some other
> license might not.
Those licenses are contracts you must agree to. They go further than
copyright law (and they may be held unenforceable, as already
discussed).
> That's why I didn't understand the first article that said you could
> modify NT regardless of license. Now it seems no license covers
> private modifications because they are not prohibited by copyright.
Actually, many proprietary licenses cover use, even if use is not
covered by copyright law. Same license/contract issues.
> So the conclusion is you don't need a license to use, read or
> decompile a program. Even to modify it privately.
> You only need it to redistribute it. But if you sign (or otherwise
> legally accept) a contract then you're bound by it (to the extent
> the contract clauses are enforceable).
Exactly. You can sign away any right with a contract (module
enforceability).