I'd have to guess that he is in fact a very skilled software developer. Minecraft is a fairly complex project, as is emulating a 16-bit CPU within the constraints of a game environment.
And I'm curious, what wouldn't you hire him for?
I've seen his posts about how git is too hard to learn[1] so he's going to stick with svn. I've seen him post that "we've started to bring in bug fixing into the development method"[2], and then the very next release is a "bug fix" release which causes more new bugs than it solves.[3]
I wouldn't hire him for a software development job that required any level of maintenance. He's good at creating original fun concepts but not at making it nice for people to read, modify, or maintain his code.
Also, I would argue that emulating a 16-bit CPU within the constraints of a game environment is easy and straightforward. For one, it's ridiculously simple to do test driven development without any overhead. And second, have you seen all the emulators that have cropped up after the specs were posted? There is already an emulator for almost every popular programming language.
[0]: https://github.com/superjoe30/mineflayer [1]: http://notch.tumblr.com/post/2623477410/strategy-meeting-day... [2]: http://notch.tumblr.com/post/4423138657/11-11-11 [3]: http://www.minecraftwiki.net/wiki/Version_history (might have to view history)
I agree that git is hard to learn and also that emulating a 16-bit CPU is straightforward.
"Oh, and I’ve finally committed the Music Blocks to the repository.
(Oh, wait, no, I didn’t.. Doing so broke git, so we’re changing to svn because git is horrible and evil)"