I just e-mailed them. I've tried it with multicard (Ak2 and Ak2) and one Ak2 to host with the other using "DS download play", and both yield the same results.
On the AK2 Wiki they say that download play works with clubhouse games, so I tried to host with clubhouse games. The host DS says "Wait until download is finished"; however, the other DS I guess already finished downloading. The black nintendo sign goes up, and then it turns gray after a split second and freezes.
Also, I'm using the beta AKAIO firmware. I'm going to try to use the firmware on the AK website to see if that works.
Edit: It doesn't, at least for me. I also tried going on WFC, but it makes my DS freeze after a few seconds. It does this on both AK2.