For Clarity’s Sake, Please Don’t Say “Licensed under GNU GPL 2” (2017)

Developers had released a new version of a program under a different license, and maybe they had made new releases of old versions offering use under a different license, but they had never set up a systematic way to offer users the choice of using a future license version for already-released versions of a program. Because we handle license compatibility this way, when people tell you a program is released “under GNU GPL version 2,” they are leaving the licensing of the program unclear. When sites such as GitHub invite developers to choose “GPL 3” or “GPL 2” among other license options, and don’t raise the issue of future versions, this leads thousands of developers to leave their code’s licensing unclear.

Source: www.gnu.org