While it's currently still in heavy development, OpenTESArena is another great example of what can be done with open source with it reimplementing The Elder Scrolls: Arena in a modern cross-platform game engine. It requires a copy of the original game for the data files, which you can get free officially.
It's not quite playable — yet, but it is showing massive promise and a new release is out now.
You can see the new release video below:
Here's the release highlights of what to expect in version 0.14.0:
- Weather effects (rain, snow, thunderstorms)
- Screen-space fog is unfinished and should be in a future release.
- UI system redesign (model-view-controller pattern, text rendering redesign, texture allocation redesign)
- Input system redesign (generic input action listeners; easier to add key bindings and more input methods later)
- Updated in-game debug profiler
- DPI-awareness on Windows (allows for native window resolutions on high-DPI monitors)
- CMake build configuration improvements (replaced Debug/Release/RelWithDebInfo/MinSizeRel with Debug/DebugFast/ReleaseGeneric/ReleaseNative)
- Updated OpenAL Soft version to 1.19.1
- Updated SDL version to 2.0.9
- Updated WildMIDI version to 0.4.4
- Fixed "Some intro screens might be using an incorrect palette"
- Fixed "The game will crash during the Ria Silmane cinematic in the CD version if it reaches the end without being skipped (related to chunk system)"
- Fixed "The automap colors voxels outside of city bounds that should not be considered part of the automap"
- Revised release build naming convention
For the next version the plan is to have a "minimum playable" starting dungeon, with an initial combat implementation to go along with it. Even bigger is the plan to overhaul the 3D renderer to allow for some more advanced techniques, initial inventory management and more.
Check it out on GitHub.