Since everyone has been asking for DSemus lately, I decided to make a guide for how to make your own. It's quite simple actually.
The entire no$gba is written in a mid-level programming code called 'assembly code'. Here is a link that will teach you how program things on your own in assembly code:
Lol, you might be able to give them a help, but learning assembly needs more help than that. The reason why is because assembly is also considered REVERSE ENGINEERING! :P
Oh well. I suggest a good book or a buddy who really knows ASM(Assembly) because if you know ASM you can do many things. And i literally mean many things.