@terhechte Thank you for releasing your software as free software (I will pay $1000 to anyone who can find the word "open" in the GPLv3: https://raw.githubusercontent.com/terhechte/Ebou/main/LICENSE).

Please note that it's good you've at least written "Ebou is licensed under the GPL License" in the README, seemingly allowing any version of the GPL to be used, but it's recommended to place a copyright notice at the top of every nontrivial file to make to crystal clear what copyright terms are and also to prevent the sad case when individual files are copied and reused without it being known what the license is (as no license sadly means proprietary).

As recommended by the GPLv3, the notice should be:
<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/>.


But you can be lazy and do the bare minimum (which is better than nothing):
// SPDX-License-Identifier: GPL-3.0-or-later
// Copyright (C) <year> <name of author>