Hi,
have a look at this:
http://www.google.com/support/forum/p/sketchup/thread?tid=74deeae241b00f82&hl=en
In general, the purpose of 3d warehouse is sharing and the ToS imply that what you want to do is allowed. For a detailed and correct interpretation of the [url=http://sketchup.google.com/intl/en/3dwh/tos.html:12hwmeqr]Terms of Service[/url:12hwmeqr], you would need an attorney. Best is always to ask each modeler to be sure if he is ok with redistribution (you can contact the owner by clicking on the model page on the envelope icon next to the author's name).