Under Armour's brand is rising. They signed Jennings and Kemba this year, both similar players who play with that "it" factor. Cam shares that as well. Its smart for a company that is rising up as someone alluded to already.
They do make shoes btw, Jennings has his "Bloodline" shoe out right now.
Jordan isn't an idiot for not signing either. Not signing the two rising stars in Charlotte to his own brand isn't going to hurt the future endeavors of the Panthers or Bobcats. In fact, with both being with UA I think it will help more than if Kemba was with Jordan Brand. A dual advertisement in downtown Charlotte would be one of the greatest things ever.
I think this whole "MJ owns the Bobcats so his players should be signed to Jordan Brand" is a little overblown. The only brand I'm concerned with them wearing is one with a Bobcats logo on it. Jordan Brand has its share of stars already signed to it, let Cam and Kemba do their thing with UA and potentially become the face of that brand.