Charter Members are those who signed up with the board first went to pay and have kept their memberships current since then. Except for occasional acts of mercy, if you let your charter membership lapse it is gone for good.
Every so often the system hangs up on a member subscription and carries it forward through it’s expired. Some weirdness happens and the flag doesn’t get dropped on expiration and so the status continues.
Doesn’t happen very often but this is not the first time I’ve seen it.