Usage of an image without permission is stealing, technically, legally or however you want to look at it, even if the copyright bar is displayed. I'd be sending them an invoice for website usage. Why would organizations pay some of us for using our images on websites if it was legal to use them without permission?
Photographing aircraft since the Earth was flat and on Airliners.net since #338
They are linking it in their forums, not posting it as theirs. More likely than not, they are linking it directly to the a.net image, so every time someone opens the page, it generates a hit on the picture! Besides, we post pictures in the Non-Av forum all the time, is that not the same thing?
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
Just because you link the URL to the image's path on the A.net server, it does not mean you are accumulating hits. The reason (regardless of right or wrong) they saved the image to their own server is because it appears like you can't "hotlink" images from A.net (you need to run a certain script within a certain script, I don't know the details). This isn't "stealing" in the sense it is normally applied here, but they should have just provided a link.