OpenXcom

An open-source clone of MicroProse’s UFO: Enemy Unknown (X-COM: UFO Defense) and X-COM: Terror From the Deep, written in C++/SDL with a large mod ecosystem.

An open-source clone of MicroProse’s UFO: Enemy Unknown (X-COM: UFO Defense) and X-COM: Terror From the Deep, written in C++/SDL with a large mod ecosystem. The upstream README describes OpenXcom as an open-source GPL clone of UFO: Enemy Unknown and Terror From the Deep in C++/SDL. Installation requires vanilla X-COM resources and warns against modded resource packs. No REA involvement is claimed. Original X-COM assets are not included and must be supplied by the user. Compatibility depends on unmodded resource files. Bundled SDL_gfx-derived code is LGPL with author permission (per README). Submitter reviewed public README/license only; we have not independently tested it.