Earlier quoted context omitted.
Well, they payed for this text to be included in the game (for further distribution, obviously). That's a bad legal definition. It needs a clarification which usually comes in a form of a contract. Mojang clearly acted un-professionally: there's money on the table without a clear job definition. What happens with the copyright? Authorship? Should the author be mentioned in the game? etc. Same goes to the writer, obvi…
> Well, they payed for this text to be included in the game (for further distribution, obviously). They paid for the deal they agreed on as described in that first email. We don’t know the contents of that email, so it’s impossible for us to know if it they agreed on just including the poem in the game, transfer of copyright or anything else.
But there no "just including" in legal speak. "Including" means some sort of copyright transfer or a license.
Either way, the text was created specifically for inclusion in the game and was payed for by Mojang.