It doesn't sound like he coded all that much from the post. He even mentions that Cactus is a little bit too much work since there's not much of an existing community surrounding it. I was just surprised that it was the CTO of Amazon after I read the post.
Actually I did do some coding for the conversion, etc. :-) But I like it when doing something new to be able to look at how other people solved similar problems. And it is a bit early for Cactus in that respect, and Liquid feels much simpler than Django templates.
The extension and plugin mechanisms will make it easier for me to start adding my own code without having to modify the core framework. But it is always more fun to add these kind of things if there is a community to give you feedback.