Not difficult really just the one answering you is indecisive at best :P. As for most active I am not quite sure how to answer that. Our top posters are not necessarily our most active posters and our top topics are mostly our games >.<
Our current most active members that I am seeing are Zane, Nightwind, Winters-Feather, Wolfie, and myself. (If I have forgotten someone please feel free to put me in the stocks for the day). We are the ones usually on and posting everyday or every other day if we have posts to reply to. Others such as our very busy admins post once every week as they understandably handle other duties as well.
However, threads by these individuals I would classify as the most active. I apologize in advance for when you find all of my threads. I really love threading and do so with everyone who is willing. As such....I have the bad habit of collecting all the threads. *Hides behind a stack of books* Sorry!
Hope this is a bit more helpful.