Have you heard about a WebGL game engine called PlayCanvas?
First of all, it lets you use javascript to create 2D or 3D experiences that are said to be compatible with most modern browsers and devices. The team also states that the toolkit features a very small engine footprint optimized for high performance, even when it comes to older mobile devices. PlayCanvas is javascript-based, and you can use standard browser development tools to debug and profile applications
The PlayCanvas Engine gives an incredible performance, even on devices such as the iPhone 4S.
PlayCanvas ensures a fast loading time by using multiple features such as script concatenation, minification, deferred loading of non-essential assets and more.
PlayCanvas has many team features such as being able to chat with your teammates directly from within the Editor.
The PlayCanvas Engine is open sourced on GitHub under the MIT license.
You can learn more about the first official version here.