Hi,
At this time we do not have a direct integration with Google sites, but they are aware of the customer request. We have heard there are a few ways to add GWD content to external sites: you can copy the generated HTML (markup, styles and javascript) into the site, or you can include the GWD generated content as an iframe into the site.
Hope this helps and when we have more to share regarding Google sites I'll be sure to post.
thx!
jaz
Jasmine Rogers
Program Manager, GWD