Gaijin Entertainment, a former Russian computer game developer, has opened the source codes of the Dagor Engine, which is used to create the multiplayer online game War Thunder.
The source code is available on GitHub under a BSD 3-clause license.
Currently, Windows is required to build the engine.
Also this engine taken as the basis for the announced open cross-platform engine Nau Engine, announced as an alternative to leading solutions from Unity Technologies and Epic Games.
Source: linux.org.ru