Bevy

ECS means you build game objects by composing data components rather than inheriting from classes. It's a fundamentally different way to structure games, and it's fast.

Apache 2.0, pure Rust. The feature list includes 2D and 3D rendering, audio, asset loading, UI, animation, and a scene system. Hot reloading lets you change assets without restarting. The plugin system means the community extends everything.

Fully free. No paid tier, no royalties, no revenue share. Apache 2.0 means you ship commercial games without owing anyone anything. That alone differentiates it from Unity's licensing drama. Solo indie devs: the primary audience. Small teams comfortable with Rust: viable. Medium to large studios: not ready. Bevy is pre-1.0 and the API changes between releases.

The catch: Bevy is pre-1.0 and the API breaks regularly. Migration between versions is real work. The Rust learning curve is steep if you're coming from Unity/C# or Godot/GDScript. There's no visual editor yet. Everything is code. And the ecosystem, while growing fast, is a fraction of Unity's or Godot's. You're betting on the future here.