So... I stumbled across this.

I was wondering it multiplayer and/or redstone could be added to it.

Problem #1: What language is DSCraft written in?

To do list:
1. Figure out the language (SmileBASIC).
2. Learn SmileBASIC.
3. Add redstone.
4. Test, revise, test.

If anyone has a DS/DSi/DS XL/DSi XL/3DS/3DS XL and wants to test the game in the future, please PM me.

Haha, good old DS programming. I did that quite a bit back in the day. Most programs for the DS are written in C using devkitPRO, available here: http://devkitpro.org/

You will also need the low-level libraries for interfacing with the DS, mainly libnds (I believe it comes with devkitPRO, if I am not mistaken).

In addition, there are quite a few tutorials out there to help you get started, in addition to some very handy graphics libraries such as PAlib. Simply browse around and look at some source to get inspiration.

And I would highly reccomend No$GBA as an emulator of choice, it is pretty handy: http://www.emulator-zone.com/doc.php/gba/nocashgba.html