I would throw an extra one in there.
There was a port of linux to the DS, going by the name of DSlinux. Such things can be useful if you are looking for staple programs of linux/unix environments, even more so if you want to chain a few together.
Did even see it reduced further still to almost be a... not really a library and not really a hypervisor or thin VM but something in that whole sphere for stuff like the standalone fsck port.