These are some of my notes I put together a while back

How to implement Open Source licenses on your software | QuantumWarp

So this information will not go to waste, and again thanks for your time.

    <one line to give the program's name and a brief idea of what it does.>
    Copyright (C) <year>  <name of author>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

Seems pretty straightforward to me. You put the “block comment” syntax for your language around that block, fill in the <one line..,> and <year> <name of author>

Since the template you used probably already had the copyright, you most likely just need to change the intro line comment and the copyright line comment.

I’m not sure what more you want to see? Here’s how I did it in my CollectionInterface plugin: https://github.com/pryrt/NppPlugin-CollectionInterface/blob/main/src/PluginDefinition.cpp:

/*
    Copyright (C) 2025  Peter C. Jones <EMAIL@REDACTED FOR ANTISPAM>

    This file is part of the source code for the CollectionInterface plugin for Notepad++

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

So when I did that, I didn’t bother with the <one line>, and I just filled in the year and name as prompted.

One more thing:

how I handle the already present copyright information

For files from the template that I didn’t edit (other than maybe changing a string or two), I just left the copyright notice as originally given (which shows it was from the template). For files new to me, or that I changed significantly from the template version, I updated with my copyright block from above. You can navigate to other CPP files in that same repo I just linked you to in order to see more files, to see my mix of notices.

If you knew of a well formed “real” plugin I can look at it and use that format. Practical examples are what I am after.

But either way I appreciate your help.

@shoulders said:

I was particular interested in should i put it on individual files like the cpp and header files.

Which is what the section I linked you to describes how to do. As I said, “that explains how to put the copyright notice in your source code”. So follow that link, and it will show you the boilerplate to put in your source code files.

If you put the GPLv3 license text in a file called LICENSE or LICENSE.md in your repo root, then GitHub will be able to make it clear to people who look at the repo what license you are under. (For best results, if you take the plain text or markdown files directly from the GNU website, GitHub can unambiguously recognize which license you are using.)

Also, the official GPLv3 page has a section that explains how to put the copyright notice in your source code, so that it points to the license.

Some plugins will also include at least the copyright notice and sometimes the full LICENSE text in their ABOUT dialog or similar, but that’s not universal.