http://www.glidingmagazine.com/FeatureA ... asp?id=215
Looks like he was 'ripped off' to make and sell a limited edition stamp, which made money, and he took it no further.I am not sure how much gliding activity there is in Bulgaria, or how many good photos would have been available, but the Bulgarian Post Office’s designer, Emilian Stankev, “borrowed” Claus-Dieter’s photo and used it as the design for one of their Bulgarian stamps. (See photo on the left.)
When asked, Claus-Dieter just said: "No they did not ask me; but if they did not have a good photo to use, I would gladly let them use mine. But they should have at least asked".
I could have understood persuing that case as it's exactly what the laws are to protect.. someone else gaining from your hard work for free.
That makes it doubly odd that he'd persue such a harmless instance of potential copyright breach (I say that as I've not read the full details and couldn't work out if you had asked before hand or not).
My first thought was have you verified that the emails where not spoofed, but you've received snail mail as well.
edit: it seems some of the profits made went to some form of sports foundation.