It's all but forgotten now, but the early statements that Minecraft was going to be released as open-source really hint towards what might have been, and the magnitude of what was lost:

"Once sales start dying and a minimum time has passed, I will release the game source code as some kind of open source. I'm not very happy with the draconian nature of (L)GPL, nor do I believe the other licenses have much merit other than to boost the egos of the original authors, so I might just possibly release it all as public domain."

https://web.archive.org/web/20120614004339/http://www.minecr...