Christian Jodar wrote:
If I have confirmation that GPL can be used to have creators credited for their works, I will contact them again with this information.
I'm not sure what you're wanting. If you want the authors credited in a derivative work's copyright section, all licenses provide this. It's not practical (and often not legal) to distribute a work without accurate copyright statements. The GPL guarantees that the author is credited in the very first section: "1 ...provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice..."
If you want to force derivative works to credit these authors somewhere else, for instance under each use of the image, or prominently in the work's description ("foo featuring images by Mr Baz"), advertising, or documentation ("This product includes software developed by the University of California, Berkeley and its contributors"), please be aware that such a restriction (commonly known as the 'obnoxious advertising clause') is not considered free by Debian, and not compatible with the GPL.
The latter /is/ a problem: if the images are not merely aggregated with your application (for instance as a sample images in an image viewer), but used in program's user interface it is likely that the image is considered part of the whole work by GPL section 2. Copyright law is more interested in artistic intent than technological method; if the image is included with a program with the intent for it to be a logo or a widget for the program, then regardless of whether it's part of the appication's binary or a separate file, it's likely that the image will be considered part of a work derived from (or consisting of; I hope not to restart the 'creative transformation/derivative work' discussion) the rest of the program's source code and the image, and not a separate work aggregated with the program.
If the images are indeed part of the work and not just merely aggregated, the GPL will only grant permission to distribute the rest of the work if the image is licensed (or licensable) under the GPL. ("when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.")
The OAC is a 'further restriction' under GPL section 6 ("You may not impose any further restrictions on the recipients' exercise of the rights granted herein"), and if you impose it, the GPL does not grant you permission to distribute ("You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License").
This would make the work undistributable unless the distributor was the sole copyright holder, or removed the images.
I read GPL FAQ and some points are not clear for me... http://www.gnu.org/copyleft/gpl-faq.html#WhyNotGPLForManuals They are telling here that GPL is not really made for something else than programs. So it makes me doubtful about using it for pictures.
The FSF disrecommends the GPL for manuals, because they don't believe manuals should be Free, and want to be able to license their manuals under the non-free GFDL, without sounding hypocritical. Their FAQ page explains their stance better than I can, but essentially they believe that a series of non-free restrictions can help authors of manuals make money and push agendas.
http://www.gnu.org/copyleft/gpl-faq.html#GPLOtherThanSoftware I am not sure that *source code* is easy to define for a picture. How should it be interpreted for it?
The source code, as defined in the GPL, is the preferred form for modification. That is to say, the form you used when you were modifying it.
If the picture was made in photoshop, for instance, the preferred form for modification is the photoshop file, and not the rendered-down PNG. If someone else edits the rendered-down file and redistributes it, the rendered-down file is the preferred form for modification.
This depends on you not lying (for instance saying that you edited it in paint, when really you've got a multi-layer photoshop file you don't want to share), but so do most things pertaining to free software: unless committed on a vast scale, most license violations go uncontested.
-- Lewis Jardine IANAL, IANADD