LayaAir HTML5 Engine
The stable release of LayaAir 1.0.0 was recently released and developers have reason to be excited. Part of the LayaBox framework, it is an open source HTML5 engine developed for high performance games. Its display render prioritizes WebGL, but for systems with incompatible graphic cards, it automatically switches to Canvas. It is designed to be lightweight and easy to use, requiring a small size installation, and running without the need for a plugin.
Get LayaAir here.