Doom World, ID Software (duh), and CodeImp, the creator of the increadibly user friendly Doom Builder 2.
New from scratch -we swear (closly based on the original Doom 2 levels) Everything was drawn from scratch and if any copy/pasting from the original maps was done ever, it was Vertices or Things only. But that was rare.
10/2009 - 6/2013
Doom Builder 2
Our custom teleport "flats" are a bit buggy in Chocolate Doom but we made sure they would not crash it. This limitation is why the teleports are so inconsistant. Also the Doomsday port shows where there are no textures.