CTR User Library library for writing user mode arm11 code for the 3DS (CTR)
the goal with this is to create a very straightforward interface with the 3DS's OS. it is not meant to provide higher level functions; to put things in perspective, the purpose of ctrulib would be to sit between the OS and a possible port of SDL rather than replace it.
you may do whatever the hell you want with ctrulib as long as you give proper credit to its authors. that includes making commercial games/apps that use ctrulib. i'd personally rather you didn't sell ctrulib itself, because that would not be nice of you, but i'm not a lawyer and it's not like i'm going to sue you.