If you own the copyright to something, then you can control the terms of its copying. Software distribution generally involves copying.
If you own the copyright, then you may control the copying directly or by granting conditional rights to other people.
If you receive under the GPL, something to which you do not have copyright, then you probably only have the rights that the GPL grants you, unless the copyright holders (all of them) directly grant you other rights.
The GPL permits re-distribution rights under certain conditions but does not permit you to add extra conditions.
So you may not take some software you have received under the GPL and place extra conditions or licensing on what may be done by those to whom you distribute.
You MAY at your option refuse to distribute the software you recieved under the GPL, the GPL does not require you to share in order to receive, but once you do use your GPL rights to share with others you must abide by the conditions of the GPL which dictate the manner in which you share.
So if its all your software you can release it in many various ways and licensing though as other people have pointed out, this is not always a good idea.
If you only received the software under the GPL and you dont have copyright, you may only distribute it according to the GPL and may not add extra conditions to those you distribute it to once you have distributed it.
I think you are tryng to see if the xtcommerce3 author is permitted to make changes; the answer is: if it is his code.
If you are asking what changes you can make to the license, the answer is: none unless it is all your code
It seems from what you are planning to do, that unless you need to be certain of the license under which xtcommerce3 is distributed to you under. After receiving your distribution of xtcommerce3, if there is any doubt about this you should, perhaps, consult a lawer that specialises in copyright law.
It is possible that the xtcommerce3 author is not aware of the full implication of the GPL, many authors are not. Maybe your act will cause the author to change the license?
Sam
Kein Ende wrote:
Hi folks,
is it allowed to make changes in the GPL down the GPL-Copyright preamble in a licence-file?
Isn't it so, that the GPL guarantees us, that all under this preamble has to be free for all?
Now I want to change the properties so, that anyone who wants to copy, distribute oder sell my software, has to ask me before.
Can I do so, or is this not allowed by GPL?
GNU GENERAL PUBLIC LICENSE
Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users.