I'm going to place my app (a dictionary) under the GPL Licence. I don't care if everybody changes the source code, fix bugs or add some new features to it; but I don't want developer changes donation link for his own. Is there any way to handle this problem? Of course I'm fairly new in open source and it's possible to have wrong misinterpret. Anyway I need enlightenment.
No, this is not really possible.
The next closes thing that you could do is to add an additional term under GPLv3 section 7:
- 7(b) to require the “preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it”
- 7(c) to prohibit “misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version”
While you can prevent someone else presenting the project as their own, you cannot really prevent them from changing a donation link. Such a link is not a legal notice or author attribution. You can put such a link next to attributions, which might deter changes.
However, a link to the project homepage might be part of reasonable attribution. You could then have a section about how to support the project on that page.
The GPL does not allow you to prescribe how such notices shall be shown. There are widely accepted practices about this, but none require that the notices be highly visible. For example, desktop applications often have such attributions in a help menu item.
While we may want to use copyleft licenses like the GPL in order to deter commercialization by others, that won't quite work and is undesirable in the long term.
- the intent of the GPL is to ensure freedom for end users, not to prescribe software pricing (sounds silly, but there actually was a lawsuit arguing the GPL was an illegal price-fixing scheme to devalue software)
- the GPL explicitly allows copies to be sold
- capturing the monetary value of the software may feel fair right now
- but what about contributors, what is their fair share?
- what if someone overhauls the software a decade from now, with your remaining contributions being minor. Would it still be fair if they are not allowed to add a donation link?
There have been recent attempts at licenses that address these issues. For example, the SSPL effectively gave the original developer a monopoly on commercially running the software as a service. The Convertible Free Software License had a threshold of changes where a new maintainer could take over ownership from the original authors. Both licenses have been criticized as discriminatory, and were retracted or rejected from review by the OSI.