How to put a software under GNU GPL code with portions licensed X11 (MIT) [closed]
https://stackoverflow.com/questions/11816461
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I created a software that is made from sources licensed X11 and I wanna put my software under GNU GPL. I know it's possible, because GNU GPL is compatible with the X11 licence. However, I wonder how to do it concretely because a passage in the X11 license bothers me:
"The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software"
So, what should I do? I just need quote the names of authors or I have to put a X11 licence (while I do not use it because my software is under GNU GPL)?
Solution
Let's say you did not modify the X11 source code. You sure need to comply with the license terms which require you to pass along the license text and the copyright statement.
So keep these items in, otherwise you would breach the usage terms and loose the right to make use of that code.
If you then add modification to that part of the source-code it depends on what you aim for. Do you want to allow your modifications to be used in the upstream project? If yes, take care that you put your modifications there under the X11 terms as well. Naturally you can add your own copyright on top because you are an author of that part then, too.
This by the way is normally suggested. Free software works by exchanging software, so be a good citizen and do not block passing improvements back (e.g. when that X11 code is some library).
You can however license your changes under the GPL, that is possible with X11 code, too. However this will prevent that your improvements can flow back upstream. So you should know what you do here and why you do so.
You find the whole topic explained with a lot of detail and some examples in this paper:
