OMG… I can’t believe it. I still can’t believe it.
First of all, congratulation to John the first author of jQuery and still the leader of the project. Although I haven’t found any articles regarding why the Google Code team chose jQuery, but here’s a pretty eduacated guess of mine based on this quote by DeWitt Clinton:
One of the most exciting things about the redesign is that everything you see here was built using technology and APIs that are available to everyone. The pages we’re serving don’t rely on any secret back-end tricks; the site is built on plain HTML, JavaScript and CSS, each using our public APIs. In fact, all of the techniques used on Google Code can be duplicated on your own site.
They are here to prove that you don’t need to have the full blown GWT to put together all these great APIs. It can work with the technology we are used to.
For those of you don’t belive that jQuery is used, got to http://code.google.com and do a view source. You will see the magical “jquery.js” 
Full Story
http://google-code-updates.blogspot.com/2007/11/my-how-weve-grown.html
Official jQuery Team’s comment
Ajaxian Post
http://ajaxian.com/archives/google-code-revamps-with-jquery
Screen Cast
Google Code Revamp from Dion Almaer on Vimeo.
