Can I publish a book and source code in the book under different licenses? Can I publish a book and the source code in the book under two different licenses? Eg. Publish a book under the GNU FDL license, but license the source code examples in this book under the Apache license?
As long as you own the copyright to the works, you can even publish the source code itself under two different licenses, which can be radically different. For example, MySQL is licensed under both a commercial and an open-source license. Given that you can publish a single piece of work as multiple licenses, it is your choice which one you wish to grant to the book or the code, as long as you own the copyright.
If you create a new work that is derived from or based on someone else's work, it is a derivative work, and you cannot do so without permission from the original copyright holder. If the original work is made available under a CC-BY_SA 4.0 license, you have permission, but it comes with conditions. One of those is that you must attribute the original work -- you must say what work yours is based on and who created it. Another is that you must license your own derived work under the same CC-BY-SA license (or a compatible one). This does not mean that your work is not copyrighted -- it is. But it does mean that you must grant to others the same rights that the creator of the work you used granted to you. That is what the "share alike" or SA part of the license means. if you don't like that, you should not use a work licensed under CC-BY-SA terms to create your own work. If you publish your work but fail to grant that license to others, you are infringing the copyright of the work you used, and could be sued. Note that if you had created a compilation rather than a derived work -- for example if you created an album of images from various sources, some of them under CC-BY-SA licenses, you would retain a copyright on the collection as a whole, and that would not have to be under CC-BY-SA. But in this case you say that you used the other person's image as a background for your own illustration. That is creating an "adapted" or derivative work, i am fairly sure, and invokes the share alike clause of the license. You might also want to consider the different case mentioned in If I include an unmodified CC-BY-SA work in a book, does the whole book have to be CC-BY-SA?
Not necessarily, but also possibly. Google Books may (or may not) have a license to distribute images of the book covers in question. This license would be between Google and the owner of the copyright of the book cover. Just because Google has a license to distribute the image of the book cover to you does not mean that you have a license to distribute the image of the book cover to your customers. However, depending on jurisdiction, using the book cover to identify a book might also be legal under relevant fair use statutes. It is also possible that the particular book cover is not protected by copyright. For example, a particular book cover might have entered public domain. If this question is not a hypothetical, you should probably consult a lawyer.
If you have released software under the LGPL license, you have given all recipients the right to modify this software for any purpose, including removing or adding features in a manner that you don't like. If you don't want that, you should not release your commercial features under the LGPL. Things you could consider doing: Publish the software under a different license. This is what you're thinking about. But note that you can't just add such license terms. Either, the license is still the LGPL with some extra terms. But then, the terms of the LGPLv3 allow recipients to remove the additional restrictions. Or, this is an entirely separate license. But then it would no longer be the LGPL, and no longer be an Open Source license. Whether such additional terms create a separate license or can be removed from the license is currently being litigated in the US in the context of the Neo4J database, which added the &quot;Commons Clause&quot; restrictions to the AGPLv3. See a discussion of the case from the Software Freedom Conservancy here: https://sfconservancy.org/blog/2022/mar/30/neo4j-v-purethink-open-source-affero-gpl/ Remove the restricted features from the LGPL version and maintain a separate commercial version, or implement the commercial features as a plugin. This is sometimes known as an “open core” business model. Due to the limited copyleft effect of the LGPL, you can still combine the proprietary parts and the LGPL-covered parts into a single program, but doing so may be confusing for users. It should be absolutely clear which parts are LGPL-covered, and which are your proprietary parts that cannot be modified. However, you would not be able to prevent recipients from using the LGPL-covered parts without your proprietary components, i.e. they would always be able to remove any licensing checks etc. More generally, it could make sense to think about why you want to publish any part of the software as Open Source. Sometimes, Open Source licensing is a good business decision, sometimes it isn't. If you want to control what users can do with the software, Open Source licensing is not a good fit for your goals.
The copyright holder is free to release the work under whatever licenses the copyright holder wants, in the absence of a contract saying otherwise. A copyright holder could sign a contract not to release under another license, but otherwise I don't see why he or she would waive the rights. The copyright holder can always decide not to reissue under a different license. The copyright holder basically retains all rights not specifically signed away. Everyone else is limited to what copyright law allows and to what license terms they have.
Bob is not authorized, but he may legally do so (in the US, you don't need specific authorization to perform a non-forbidden act). In creating the manual, Bob would need to avoid reproducing the questions (which are protected by copyright), and just give the answers. Copyright protection for the textbook includes not just the actual words, but also organizational structure, so Bob would need to avoid copying the structure of the exercises. As for "structure of the exercises", textbooks often have exercises for each chapter, with a clear logic to the order and content of chapters. Within the chapter exercises, there is often some rationale to the order of presentation of the dozen exercises, like starting for with simplest concepts presented in the text and moving up the ladder. In a given exercise, there my be subparts, where understanding part 1 leads you to understanding part 2, and so on. In a well-structure textbook, maybe 20% of the creative nature of the book is that artful ordering. Imposing an entirely different order on your solutions avoids copying the author's protected expression.
The creator of the software doesn't provide any warranty. If you feel confident in the quality of the software, nothing stops you from providing a warranty. If the software doesn't meet your guarantees, you will have to pay out because you provided the warranty, depending on the terms. Not the creator of the software because they explicitly didn't provide any warranty. If that's what you want to do, go ahead. I wouldn't. You don't have to republish under the BSD license, which you wouldn't. You must attach the license terms, which clarifies the role of the original creators, and that they don't give a warranty. Doing this allows you to copy the software. It doesn't mean you can't provide a warranty.
The GPL does require you to keep any existing copyright notices: You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you [...] keep intact all the notices that refer to this License and to the absence of any warranty [...] The GPL also recommends adding a notice to each file: Copyright (C) yyyy name of author - This program is free software[...] From my reading of the GPL, if the software you modify contains such notices, which is likely, you must preserve them. This effectively attributes the original author. However, as far as I can see, there is no requirement to have a list of acknowledgements (as is customary in scientific papers), which lists all the software you used. How to attribute parts that are integrated in source form? (Where licence information is given in the file header) If you keep the original file header (and possibly add to it), that should be enough. How to attribute parts that are integrated in binary form? As far as I can see, there is no additional attribution required for distribution in binary form. The GPL requires you to supply the source code along with the binary form, so the attribution in the source code will be available.