OpenMW

OpenMW is an open-source reimplementation of the engine behind The Elder Scrolls III: Morrowind by Bethesda Softworks. It is a free engine, not a free game: you must own a copy of Morrowind and supply its original data files, which OpenMW then runs in place of the aging original engine.

The main quests of Morrowind, Tribunal, and Bloodmoon are fully completable, and OpenMW adds modern conveniences such as improved graphics and user interfaces. Compatibility with mods built for the original engine varies, since its script compiler checks more strictly. The package also ships OpenMW-CS, a drop-in replacement for Bethesda's Construction Set for editing and creating content.

OpenMW runs on Windows, macOS, and Linux and is licensed under GPLv3. Its scripting layer also opens the door to new standalone games built on the engine.