zSim

zSim is an excellent flight simulator that caters to both RC-models and real aircraft, with a particular focus on gliders. It boasts a full 3D renderer, based on OpenSceneGraph, which provides a realistic and immersive flying experience.

One notable feature of zSim is its licensing and distribution under the terms of the GNU Library or Lesser General Public License (LGPL). This ensures that the software is open-source and freely available for anyone to use, modify, and distribute.

The simulator's interface is user-friendly and easy to navigate, even for those new to flight simulators. The controls are intuitive and responsive, and the graphics are stunning, creating a breathtaking view of the virtual world.

For those interested in gliding, zSim provides an unparalleled experience with its dynamic thermal simulation feature. This feature accurately simulates the behavior of thermals and allows the user to fully explore and appreciate the beauty of gliding.

Overall, zSim is a top-of-the-line flight simulator that is sure to satisfy any aviation enthusiast. Its focus on gliding, realistic simulation, and open-source distribution make it a must-have for anyone interested in the world of flight.