DDT is stated for "Decision Diagrams for Ternary". This is open source synthesis and simulation tools for creating ternary hardware based on ternary multiplexers and it's developed by Alexander Shabarshin since 2010.

Historical location of original source files: http://nedopc.cvs.sourceforge.net/viewvc/nedopc/src/ddt/ (last update in 2011).

New git-repository with all recent updates: https://gitlab.com/ternary/ddt