[redwall_hp]

This is how the Bukkit disaster happened. Microsoft "bought" the leading Minecraft server software, hiring some of the major developers and I guess not telling anyone else, and some of them were unamused that they were (in their eyes) doing free work for Microsoft when their colleagues got hired. So they rescinded their GPL licensing of their contributions and sent DMCA notices. Which pretty much ended the project, except for Spigot continuing development in the form of patches that the server operator applies with a script.

[ericpauley]

It should be noted that the authors didn't rescind any licenses, per se. Rather, distributing binary versions of Bukkit was always in violation of the GPL (since the bundled Mincraft code did not have source available). The former author simply started enforcing this. Important distinction since rescinding the license would be a far more legally/ethically dubious action.

[franga2000]

*Mojang, not Microsoft. EvilSeph was hired in 2011, Microsoft bought Mojang in 2014.