I only keep stats for sheep/peehs variants. In that regard, xander has hosted the most individual games comfortably last year and marginally this year.
However, stats are not always the full story as JMurder's 200q game is still only counted as one game, and Booker and Arctic have held weekly or almost weekly games this year. DM, IBD and others have also run many great games.
There are many other games like ww, quiz games, paint games, thunderdomes, chess thread, etc. that require varying degrees of time and effort to put together and keep running smoothly so I'm not sure anyone could definitively say who is the most active mod on POG.
I personally do it because I enjoy it, and try to make good games, and I'm grateful that others make games for me to play in too.
PS I'm not the official anything, but I did get JM#1 to give me this nifty undertitle