Clam's, Rubix's, and the lemforum pack were most active in 2012 and 2013. Clam has released updates for his Lix, pack, but I haven't looked at those updates yet.
The quality of the Lix level packs is massively ahead of the quality of the core game. Clam has updated his pack, NaOH has released her forest tileset. The C++/A4 game got framestepping, and the D port looks as if it's got about half the features from singleplayer done. Despite being a massive technical jump forward, this hasn't yet produced shiny releases. It's reasonable if the cultural output has been way less in 2015 than usual.
-- Simon