Thanks. The policy at IS is (untypically) very clear.
It's very clear to me. I use one of the NASA globes regularly as part of a composite shot, and I never had problems with it, on any site. The latest one is here:

My main banner on
FD has a globe on a beach too. You just can't resell NASA shots "as is".
By the way, there is a guy on DT that has fantastic pictures of the space shuttle. He is clearly an insider since some viewpoints are not open to the public (I guess). Portfolio link
here.