GNU GPL GNU GPL v2 GNU General Public License Version 2 https://www.gnu.org/licenses/license-list.html, accessed 23 June 2016. The GNU GPL v2 is an earlier version of the GNU GPL: a free software license, and a copyleft license. Please note that GPLv2 is, by itself, not compatible with GPLv3. However, most software released under GPLv2 allows you to use the terms of later versions of the GPL as well. When this is the case, you can use the code under GPLv3 to make the desired combination.