HexChess is a hexagonal chess program powered with the Godot Engine. It includes several variants of hex chess (Glinski, McCooey, Hexofen) as well as peer-to-peer multiplayer. Currently, it doesn't have any AI options.
To manipulate the source code you'll need Godot 3.5.1 or later. The code is licensed under the MIT license, feel free to use it in your projects. However, there are additional restrictions on some assets, check subdirectories for more info.