Topics: Independent Developers : Flight Gear

Taken from the official site.The Flight Gear Flight Simulator project is a free, open-source, multi-platform, cooperative flight sim development project. Source code for the entire project is available and licensed under the GPL. The Flight Gear project is working to create a sophisticated flight simulator framework for the development and pursuit of interesting flight simulator ideas. We are developing a solid basic sim that can be expanded and improved upon by anyone interested in contributing.