Al and Josh are the leaders of this team; Atlanta’s best two players. This is something that they have both earned with their play and effect on the team. Of course, the two were part of the triumvirate of captains with Joe in the previous seasons, so this isn’t a new function for either of them.
I think the only surprising part here is the “interim” label, which seems to foreshadow that one of these guys will ultimately be selected as the team’s sole captain. This is essentially a win-win situation for Larry Drew, as both of these guys would likely do a great job as being the team’s focal point on and off the court.
Theoretically, he could keep both of them as captains, but the interim tag would seem rather pointless if that were the case. (Of course, I tend to over-analyze things at times, so who knows?)