Who would the author be granting a license to? The project had no legal entity at the time of his contributions and the fact that some of the developers were la

Who would the author be granting a license to? The project had no legal entity at the time of his contributions and the fact that some of the developers were later hired by Mojang doesn't imply that Mojang can arbitrarily re-license the original author's code. Further, the actual license that the original author used was the GPL. I think it'd be very difficult to say that there was an "implied license" that was somehow not the GPL.