The game runs at various speeds depending on the machines. A Linux notebook managed 60fps, a Mac Pro got 45fps, and a Macbook Pro got 25fps. WebKit was able to perform the best of the browsers right now because it doesn’t have the multi-process per tab tax that means a lot of OpenGL buffer copying.
You can download the GWT Quake II Port and build it yourself. Instructions for doing it on Mac and Linux platforms are provided.