License and GPL compatibility

[Calinou]

I see that this project switched to the Academic Free License a while ago, which is not GPL-compatible according to the FSF. (It looks like it used to use the MIT license before.)

Also, the AFL isn't a very commonly used license – it was not in the top 15 of the most used licenses on GitHub back in March 2015.

Would it be possible to switch back to a GPL-compatible license? This would require an agreement from all significant contributors.