Overgrowth Game Engine Open Sourced
80.lv
80.lv
https://m.youtube.com/c/WolfireGames/videos
The title says "game engine" because the artwork remains proprietary (similar to old id games, buy the game to get it).
However, just to clarify, all the game code (including gameplay logic, which is sometimes not considered part of the "game engine") is Apache 2.0.
GitHub page: https://github.com/WolfireGames/overgrowth