I have found a nice program on GitHub that reads data from “A” and puts it in a text file, it is released under GPL3.

I want to modify it to put the data in a database instead and then release it as GPL3. I’m aware of the bigger picture of the license but has never before actually done this by myself, therefor I ask if there are any particular pitfalls and mistakes that will go against the license that I shall look out for?

Do I have to fork it on GitHub or is it ok to download the code and incorporate it to my new software?

Do I have to make any attributions to the original author besides leave the original copyright claim at the top of each source file?

Shall add my own name as a contributor to the top of files I edit and what is the proposed form for this if so?

This might be quite trivial questions but I don’t seem to find a good guide describing these hands on part of building upon existing open source code.

  • 1
    You are asking 3 distinct questions and it seems like you didn't do any research yet to try and answer them. It's better if you try to find an answer first and if there are still questions come back with your specific uncertainties about one specific area so they can be addressed. For example the question about attributions (your second question) is answered in the GPL itself as well as on this site.
    – Brandin
    Dec 20 '18 at 9:02
  • 2
    "Do I have to fork it on GitHub or is it ok to download the code and incorporate it to my new software" - This question is confusing, because it confuses two different issues. Forking on GitHub is one thing (GPL gives you permission to make verbatim copies, including 'forks', and GitHub implicitly permits you to "fork" any public repository on their site). However, "incorporating code into my new software" is a different thing entirely. If you are incorporating GPL v3 software into your "new software" you need to say what the license of the overall software will be.
    – Brandin
    Dec 20 '18 at 9:06
  • For social (not technical) reasons, you may want to propose your patch and improvement to the original author and project. forking a project may be frowned upon Jan 3 '19 at 9:03

You probably want to look at the Gnu advice page. To answer your questions,

You can grab the source and use it as you like, as long as it stays GPLv3. In fact, if you're going to redistribute a modified version, you have to have the source available. Probably the easiest way is to have the source and executables downloadable at the same place. You can have that at GitHub or any other place you like. Just make sure you never offer an executable download without an adjacent source download (it's OK to do it the other way, a source download without an executable download), because then things get more involved.

You leave the original copyright notices where they are. For any file you change, you put your own copyright notice above or below the existing ones, something like "Copyright RobinSt 2018".

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