There doesn't seem to be a clear cut yes or no based on their terms of service from google. http://sketchup.google.com/intl/en/3dwh/tos.html Base on the people who talked about in the forums here , here & here I would be inclined to say no for the users ones unless you contact them directly. But I won't claim to really understand there TOS. Archived3D doesn't seem to say anything so those could just be "acquired" from other sites or other people.
I usually stick with turbosquid or 3docean if I need to be 100% sure. or just make the model myself if I can & have the time.