good question! The conversion company seems to have had some issues converting from our "anchor" system that Les had set up - to work with the way the this forum deals with members. Will probably be a while before we figure out how member and exmember from the old site will work here. What we have now is a little messed up, but seems to be working.
“active member” is not an actual role - I think it means that the user is a member, who is active at the particular point in time you are viewing. But I could be wrong. Active might mean that the member has passed some threshold for how many visits they have made, how many posts created during a set time period, or something of that nature.