copyright and gpl

[janus]

Hi,
when i look through code (Qt OS) form others i often see a "Copyright (C) by XXX" in the header file comment. Does anybody know why this is necessary (if so)?

[wysota]

To note who is the owner of the code.

[janus]

But owning something everyone can copy, modify and distribute doesn't make much sense ... imho

[wysota]

But owning something everyone can copy, modify and distribute doesn't make much sense

GPL doesn't allow it. But even if it did, the original code would still be owned by its author and nobody else could say he/she wrote it.

[janus]

GPL doesn't allow it. But GPL means copyleft, doesn't it? :confused:

[wysota]

But GPL means copyleft, doesn't it? :confused:

Compare GPL to LGPL, BSD or other public domain licence and you'll see how "copyleft" GPL is. It's quite restrictive compared to others. IMHO the only completely free licences are those that fall under public domain and even then the original code is owned by someone, only that he/she doesn't restrict its usage in any way.

[Brandybuck]

"Copyleft" is a marketing term of the FSF. GPL code is copyrighted and owned. In fact, without the copyright, there would be no way to enforce the restrictions in the GPL!

There are two reason why copyrights are still necessary for free software. The first is it prevents other people from pretending they wrote your software. The second is that it allows you to attach a warranty disclaimer.

[amicitas]

Let me try to clarify (from what my understanding is) (IANAL though).


When you release code under the GPL your are claiming ownership of the code you wrote and giving people a license to use the code under certain conditions.
The conditions, among others:
1. That any project that uses your code must also release it under the GPL ("copy left")
2. That your copyright notice is kept intact, and that any changes to the code are clearly marked.
3. . . .

As the owner of the code, you can choose to license your code anyway your want, including selling it or giving it away. For example you could do what QT does and have a GPL license and a commercial license. If however you do not own the code, you must follow the terms of the license for that code (ie. GPL).

That is why item 2 is so important. If I were to write a piece of code from scratch I would have full ownership rights and can do whatever I want with that code. However If I include any code owned by someone else and released under the GPL I now must follow the terms of the GPL. The only way around this would be to contact the author of the included code and to get them to give the code to me under a different license.

A very large project could have many authors all who own a piece of the code. Each would have to give permission to use the code under any terms but the GPL. Since obtaining that permission would be all but impossible many large projects sometimes require authors to transfer ownership of their code over to a central agency (ie. Sun for OpenOffice.org).



So getting back to the point, if you release code under the GPL you want to put a copyright notice at the top of all of your source files so that anyone using them knows that you have ownership, and that they are free to use the code. If you use a piece of code that someone else released under the GPL you must keep their notice intact.


Now there are other ways to license code than with the GPL. Some of those ways do not have these restrictions on what other people can do with it. If you are releasing a Qt application you need to check that the license you are using is allowed by Qt. (They allow quite a few, in their source code is a file "GPL_EXCEPTION.txt" with a list of allowed licenses.)



Hmm . . . I don't know if that did much in the way of clarifying . . .


-- amicitas

[wysota]

Hmm . . . I don't know if that did much in the way of clarifying . . .

That's the problem with GPL - you can't really clarify it and only few people in the world are sure they understand it.