This is really cool, but what about adding interactivity with the charts? My first thought when I saw the headline was that this python library just generates D3 code, but it seems to be generating some sort of a static SVG object.
http://bokeh.pydata.org/plot_gallery/iris.html
That has a selection tool you can play around with.
As for the architecture, BokehJS is built entirely on top of HTML canvas. The python bokeh library sends data and plot specifications to the browser, which uses BokehJS to render the plot and handle interactive tools, etc.
EDIT: Ok, everything but the zoom works. How do you zoom?
If that is not the issue, please file a ticket on GitHub!