Right after that it says ‘© Author’, which links to a Terms page, which states “If you make money from using our stuff, share it with us!” and “You acknowledge the author, including in derivative works, if possible with a caption” and “You make an effort to contribute similar material of your own creation to the Web under similar terms, if and when you can.”

http://gallery.hd.org/terms.html

The license has enough holes to drive a tank through. They're clearly not using the image to make money. Acknowledgement is done "if possible". Contributing is done "if and when you can".

The "if possible" line is left up to the interpretation of the licensee (in this case, the NSA) and they can simply argue that it wasn't possible because the program was classified and including the name of a civilian who has no clearance might have impacted the classification status. Regarding contribution, that too is left to the discretion of the licensee... "Sorry, we couldn't".

As much as one might like to find fault with their use of the logo, I fail to see how this is infringement.

I agree, it’s all very wishy-washy and full of contradictory statements. My point was simply that there was more text than “Free to download and use”.

However, without the full slideshow we don't know as a fact that they've committed infringement.

We're working off a broad assumption that they've never attributed the author.

It says "requirement to credit and link" in the article with a link to http://gallery.hd.org/terms.html