Here you can find downloads for Wicked Engine, the free and open source game engine.

You can download a packaged version of Wicked Engine (the editor) from the Microsoft Store:

(But this version is not updated regularly, for most up to date version, get a development build below)

You can download the latest version of the development build below:

Nightly builds for Windows and Ubuntu can be found on Github

The source code is hosted on Github
The C++ documentation can be read on Github
The LUA scripting documentation can be read on Github