sgstair has his IP stack listed at 80% complete and has this to say on the state of DS wifi:
Rudimentary IP layer has been created... so now just TCP is required to make a proper demo. Should be soon. (Yes, I know I could just as easily demo with UDP or whatnot, but I'm committed to bringing TCP, mainly because I remember the gamecube situation where for the longest time the only public code was UDP without ARP.)
Maybe it should be noted that the percentages on my list are to initial completion, until I have something to show for it.
I will very likely make the source code public on initial release, but please stay tuned as I'm not going to drop this project and will release a much more polished version not much later.