Is there a formal way to state modifications of a program covered with GPL? [closed]

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So I created my own modified version of a program with the GPLv3, and it's open source and everything.

My question is how am I supposed to state that I modified it?
Do I just put in a comment saying # Modified by yentup ?

I've tried researching about this topic but I haven't found any directions on how to do so.

Answer 1

You have no requirement to say that you modified it at all - your only obligation is to offer the source code to anyone who uses your version.

However the best solution for you, the original authors and future users is probably to have your changes put back into the main source tree, assuming that they would be useful to other users! At which point you the version history would mark your changes, you could also add your name in a comment if you wished.

Answer 2

Well, I'd say this is less a GPL specific question but more about Copyright in general.

Let's make it scenario that you make copyrightable changes to the work. You are allowed to do that because GPLv3 is a Free Software License which grants you a right to copy and modfiy the program.

So let's say so far you did the changes only in code, not inside (copyright) commments or documentation files with that code.

That would mean the original copyright line is there for the whole work in the one or other form:

Copyright 2012 Jane-Original-Holder Toe

As you made copyrightable changes to the work this copyright line is not correct any longer. First of all because you did the changes this year 2013, the year needs to be updated.

Also Jane-Original-Holder Toe does not hold the copyright for the whole work alone. The information is wrong.

As you should not provide wrong copyright information (depending on where you live this is more or less controlled by law what that means in concrete), you should consider to reflect the changes in copyright (I can only suggest you that as a software developer).

So marking the modification is more or less a requirement by law, and not by the GPL v3 in specific.

One easy way to keep documentation of who wrote and committed which change when to a codebase is to use a SCM / RCS which allows you to specify committer and author, for example Git.

Also for the existing history. And also as Martin Beckett wrote, consider to give changes back upstream. Live is too short to develop alone.

Turns out, there is a lot of related material which you didn't reference in your question, so see as well:

• How should I state the changes I've made to a modified free software (Oct 2013)
• Changing copyright notice in file header when contributing to a project (Feb 2013)
• GPL copyright notice when contributing new files (Jul 2012)

and most likely some more.