While I have not open-sourced Hangman proper, its plug-in interface is open. I have here sample projects for both creating game modes and language packs. If you have any trouble, don’t hesitate to contact me.
Language Pack
(275 KB) Includes an xCode project file with header files for MSHangmanLanguage with the code to the Spanish language pack. The code used in the Spanish language pack is used with minor variation in most of Hangman’s language packs. Released under the GPL.
Game Mode
(1 MB) Includes an xCode project file with the two necessary header files along with the subclass for the sample Dictionary mode. Demonstrates how to interface with Hangman, provide localisations for plug-ins, request a window resize, and handle endurance-style games.