The article says "...But the wife of Democratic presidential candidate Barack Obama wants to make sure people know that accepting AKA's invitation doesn't mean she'd rule out others..." (
http://www.swamppolitics.com/news/po...kappa_alp.html)
It seems clear that Michelle does not plan to have exclusive membership in AKA and help the other sororities as a non-member. She wants to be eligible for membership in all 4.