UE3 in a java/HTML5 windows

[rajpoot]

What sorcery is this?

From the FAQs. Sounds pretty neat.
Edit: It is also up my browser a bit.

Mozilla is working on a new way to bring content to the Web and have it run at near native speeds. Using Emscripten to cross-compile C and C++ applications into JavaScript, Mozilla can bring large, high-performance applications to HTML5. This technology is already cross-browser as it outputs standard compliant JavaScript. The output from Emscripten also follows a stricter form of JavaScript called asm.js. It’s possible to optimize for this subset, as has been done in Firefox, to run within 2x of native speeds. Existing web standards such as WebGL and other Web APIs provide the hardware access needed to deliver incredible gaming experiences as shown by the Unreal Engine 3-powered Epic Citadel demo.