For those who can read japanese: What kind of functionality does this scripting language have? Does it have some sort of rendering/drawing and/or audio libraries?

Its main feature is that it's slow as hell, hence the name "OsoScript" (slow script). All I could discern from the technobabble was that you shouldn't have any expectations for it, it's just his hobby. Maybe that's just Japanese modesty? (sorry I can't be more helpful, I have little to no understanding of computer science)

lol that's why it called Osoi... Slow, and the Icon is snail
just what this scripting do?

Ok, I finally got around to download the damn thing and take a look. It's just a toy programming language, with a C-style syntax and an ugly function naming convention. And yes, it's terribly slow.

@MyNameIsNobody: Thanks for your help
@kesadisan: OsoScript allows you to write your own programs and run them on the DS without the need to set up a complete toolchain. Maybe it can be used for very simple games/demos but not much more. At least in its current state.