I have build an open source audiobook player which is licensed under gpl v3.
Yesterday someone sent me a mail with the topic 'Violation of source code license' including a link to an app that seems an exact copy of my app. Does that violate the license? How do open source projects normally react to situations like this?
Forking and rebranding is allowed by most open-source licenses as long as they satisfy the terms of the license like:
If they have modified or removed your copyright headers, avoided mentioning the contributions, only ship binaries not responding to source requests; you could take civil law action against them.
If you perceive violations and care about it, spin up your legal team and/or the EFF and enjoy years in court. Licenses only have power if you can enforce them. Most of the time when this happens, it's in some backwater country somewhere where you cannot feasibly go to court or have very bleak chances of winning.
It depends - on which specific license you're using, exactly how they're using your code, and exactly how they are branding or naming their software product (versus the name of your software product).
Trademark law in most countries is subtly different than copyright or license law, in that trademarks are primarily how end users perceive the name of brand of a product and what organization they believe is providing that product.
GPLv3 only slightly addresses trademarks, so the license itself doesn't tell the whole story. But typically the copying and redistribution rights that GPL and other open source licenses do not necessarily grant any trademark rights to other users.
The primary purpose of open source licenses is to allow others to use your code, even to give away or sell software products based partly or completely on your code. So it's likely OK if they are selling a new copy of your app - as long as they are not using the same brand or name for the app as you are. It's also typically OK for them to take your whole set of source code, change the name, and build effectively the whole software product to sell. As long as they are otherwise complying with the license (keeping the GPL and copyright notices in there, etc.), that's OK legally.
What is almost certainly not OK is if they are using the same name (Fibox) or a very similar name to what your project is named for it's downloads. The name of a software prodcut that you release to the public is a trademark, even if you don't register it. Even when using an open source license, you typically do have rights to prevent others from using the name/logo you used for your software.
Many open source foundations have trademark policies that make this clear: it's fine to re-use our code, but you can't reuse our name/logo/brand. See Also:
