There is no right or wrong, GPLv2 and GPLv3 are different licences. In order to make it possible to use GPLv(n) code together with GPLv(x) code, developers oft

There is no right or wrong, GPLv2 and GPLv3 are different licences. In order to make it possible to use GPLv(n) code together with GPLv(x) code, developers often use the 'or later' clause when they licence under GPL. However if they only want the code to be used under the conditions of GPLv(n) then they will omit that clause, as Linus Torvalds did with Linux for instance. The example you portray has nothing to do specifically with GPL, it would be just as true in any other licence incompability scenario. And if the original authors don't want to change the licencing then that's their right, end of story really. Again GPLv2 and GPLv3 are _separate_ licences, and incompatible with eachother _unless_ there is a clause which allows the code to be released under a later GPL version.