I don't have any experience in implementing anything like this, but as far as I know there aren't any pure python HTML rendering libraries.

On a normal linux Gnome installation you can use PyGtkMoz bindings to render HTML
http://patrick.wagstrom.net/tutorial...kmozembed.html

This probably won't work out of the box on Maemo, but since the new webbrowser is Mozilla based, you may be able to get it working (please post your findings, I would very much like to know)

There was a pure python webbrowser made a few years ago: Grail
Sadly it isn't maintained anymore, and it only supported HTML 3.2 without javascript. It doesn't function correctly on newer python releases (it was made using python 1.5 if I'm not mistaken).
So using that code as a html renderer will probably need a lot of work. http://grail.sourceforge.net/