Kinda neat, but why? Who really wants this? It runs a lot slower than a native exe, and waiting for something to load in the browser seems like a silly idea if you could wait for a real program launch.
The issue of "loading" needs to be tackled on. In that very specific case, it is just that the program was not designed for streaming of asset data. This is a technological demonstration of possibilities of running native apps in a browser. But lot of work are remaining to do.