一般而言,GNU 套件應使用最新版本的 GNU GPL,並採用「或任何更新版本」的措辭。關於授權聲明的確切措辭,請參閱程式碼的授權聲明。
有時,GNU 函式庫提供的功能可能已經透過其他實作方式廣泛地提供給專有程式;例如,GNU C 函式庫。在這種情況下,應使用較寬鬆的 GPL (Lesser GPL) (再次強調,關於聲明措辭,請參閱程式碼的授權聲明)。然而,如果 GNU 函式庫提供獨特的功能,則應使用 GNU GPL。https://gnu.dev.org.tw/licenses/why-not-lgpl.html 討論了這項策略性選擇。
這些函式庫中有一些需要與根據僅 GPLv2 條款發布的程式協作;也就是說,這些程式允許 GNU GPL 第 2 版,但不允許更新的版本。在這種情況下,GNU 套件應以雙重授權方式發布:GNU GPL 第 2 版(或任何更新版本)以及 GNU 寬鬆 GPL 第 3 版(或任何更新版本)。以下是這種情況的聲明:
This file is part of GNU package. GNU package is free software: you can redistribute it and/or modify it under the terms of either: * the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. or * the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. or both in parallel, as here. GNU package 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 copies of the GNU General Public License and the GNU Lesser General Public License along with this program. If not, see https://gnu.dev.org.tw/licenses/.
對於小型套件,您可以使用「This program」來代替「GNU package」。