Andrew Gray wrote:
They don't make any statements about political usage, but I suspect they would be v. cagey were it used to "convey endorsement" in a similar manner.
I think this is a bootstrapping issue.
It is well known that NASA photographs are available for everybody, so a normal person should not construe that their being used in an advertisement implies that NASA supports the product unless other factors weigh in.
However, photos by CNES and other agencies in France have traditionally been available on request. This means that if that photo is used in a political or commercial campaign, assuming that traditional way of doing things, then it is either used illegally (then the agency should sue, and if it doesn't then it is to blame) or the agency agreed to the deal (then the agency is to blame).
This means that if they were to free everything at once, during a transition period (that is, until everybody gets used to their new way of doing things, which can take a while) they would be exposed to blame.
(An interesting parallel: ever since Wikipedia was created, people not used to Wikipedia's openness have blamed it continuously and said the project would fail miserably. Only recently have people changed their attitude and started to take Wikipedia's openness as a fact of life. There's a transition period, which is not finished yet.)