Doom Legacy is a port that introduced several features to Doom, notably 3D floors, deep water and player skins. It also made use of FraggleScript and enhanced it. ZDoom supports some features from Legacy, with GZDoom offering nearly full-compatibility with it.
Doom Legacy was seemingly abandoned for several years after the 2004 release of 1.42. A port called ReMooD, started in 2008, aims to be its successor. Doom Legacy itself was resurrected in 2010.