From what I read on his site, he intends the game to be more of a RPG than a 'mine and build' type game. Now, of course it is going to have Mine and Build in it because he'd be crazy not to, but the main focus will be actually playing the game as an RPG.
If the landing page doesn't indicate it enough, it's a voxel game. Right now, it's just a very pretty online building game with blueprints, which are miniature, movable collections of blocks that can be used to make furniture or can be squished together to make some very intricate statues and even buildings.
When it's 'done', the general hope is that the game will have functioning ecosystems, dynamic biomes, and a fully fleshed out RPG experience without the need for a leveling system. Weapons are planned to all be custom, and most if not all actions will require skill (ie mining requires you to swing your pick a certain way to avoid shattering gems or damaging ores, smithing requires specific heats and different methods for different metals, etc). Multiple races, elemental "life energy" based magic, and other high fantasy goodies are also planned.
Life has gotten the better of the developer lately(his wife has cancer), and the immensity of the upcoming update has only slowed things further, but it's definitely worth checking out
If you wanna follow in the technical path of Minecraft you can always use LWJGL and code your own engine.
There's a Mincraft-type project called Mythruna that uses an engine based on LWJGL called JMonkey.
For me, when it comes to engines, I prefer more generic open features than really advanced features, as I find the more features an engine has, the more I need to get access to the source to under features that are forcing the game to behave in a way that I do not want them to. It just seems that the more feature-rich an egine is, the more it is trying to become a "game maker" rather than an egine.
The usual response to this is something something garbage-collection, something something heap-allocations, something something bounds-checking.
I agree though. Java seems to work well for Minecraft, and generally seems a reasonable choice.
I'm quite sure the memory requirements would be less were it developed (with comparable skill and care) in C++, but I don't think anyone's really complaining about that... I'm not a Minecraft person though, so maybe I'm wrong.
Not a good argument in itself, but the Open Source Mythruna project (a kinda-sorta clone of Minecraft) is also using Java, with the JMonkey engine.