Why do we need the emu to run both GBA and DS when there is a GBA emulator already out. wouldn't it be easier to let it play DS roms only.

Think abour that

Well there are a couple reasons why it should emulate GBA

1.) The DS itself plays GBA games so it can be for completness
2.) Programming a GBA emu would give you some good experience for DS
3.) If im Correct the DS uses the GBA core and stuff to run the bottom screen and the DS core is for the Top Screen.

Anyone know where in the source files the DSemu reads the.ini file?

As Nukefall's stated, the DS is based heavily on GBA technology, so there'd be a GBA core in the emulator anyway. It only makes sense to expose it, and let it run stuff.
Sure, the author can tell ya. Everywhere. Just do an all-file search for GetPrivateProfileString, and you'll turn up results from all over the source. The results should be mainly from glds/glgba, though.

Ah darn. I was gonna try and make a converter to read a String instead of a number like "Up" istead of the original. (I forgot it cause i changed it) That way people wouldnt have to find the ASCII keyboard standards.

Are the graphics in the bottom screen based on gba?