iOS

DOOM-iOS (C++, GPL-2.0, mature, inactive since 2012)
Esenthel Engine (C, C++, Custom, beta)
Gorillas (Objective-C, JavaScript, Java Research License, mature, inactive since 2014)
Hedgewars (Lua, C, C++, Pascal, Haskell, GPL-2.0, mature)
LÖVE (C++, zlib, mature)
NOVA PINBALL (Lua, GPL-3.0, beta, inactive since 2017)
OpenLara (C++, 2-clause BSD, mature)
ouzel (C, C++, Objective-C, 2-clause BSD, beta)