Tool

Athenaeum (Python, GPL-3.0, beta)
AutoREALM (C++, GPL-3.0, mature)
Bt Builder (C, C++, GPL-3.0, beta)
CBoard (C, GPL-2.0, beta, inactive since 2018)
D-Fend Reloaded (Pascal, GPL-3.0, mature, inactive since 2015)
Dedalus (JavaScript, GPL-2.0, beta, inactive since 2018)
Deity (Python, GPL-2.0, mature, inactive since 2014)
Doxygen (C++, GPL-2.0, mature)
Dungeon Mapper (C++, GPL-3.0, beta, inactive since 2013)
Fantasy Map Generator (JavaScript, MIT, mature)
GM Tools (C++, GPL-2.0, beta, inactive since 2004)
GoRogue (C#, MIT, mature)
Gottet (C++, GPL, mature)
JaNaG - Java Name Generator (Java, GPL-3.0, mature, inactive since 2016)
Monster Generator (Java, MIT, mature)
PCGen (Java, LGPL-2.1, mature)
Pendumito (JavaScript, GPL-2.0, mature, inactive since 2003)
pkg-config (C, GPL-2.0, mature)
Procedural Map Generator (C++, MIT, mature, inactive since 2018)
Psyco (C, MIT, mature, inactive since 2008)
Pymapper (Python, GPL-3.0, mature)
PyTMX (Python, LGPL-3.0, mature)
ReShade (C++, 3-clause BSD, mature)
rFXGen (C, zlib, mature)
Rolemaster Office (Java, Apache-2.0, mature)
Rolisteam (C++, JavaScript, GPL-2.0, mature)
RPDungeon - computer aided role playing (Pascal, GPL-2.0, beta, inactive since 2006)
SLADE (C++, GPL-2.0, mature)
Squiffy (JavaScript, MIT, mature)
Twine (JavaScript, GPL-3.0, mature)
VGC (C++, Apache-2.0, beta)
World Builder (Visual Basic, GPL-2.0, mature, inactive since 2007)