The GPL ship has sailed. It used to be every free license could be converted to GPL, so it became the "universal recipient" license. Then Stallman forked it and created two incompatible GPL's, effectively killing his own dream of a copyleft ecosystem. So the only sane thing now is "universal donor" licenses like MIT - or straight public domain. I'm stealing all of this from Rob Landley.
https://ia601008.us.archive.org/7/items/OhioLinuxfest2013/24...