My first thought was the Software Freedom Conservancy. The only reasons I see for them not to take GPG under their wing are lack of will (but why?), sense of funding priorities (but why?), or the possibility that some GPG constituents would be concerned about associating GPG strongly with a US-based organization.
There's a history of Koch that is pretty ugly. He tried to start a consulting company with said government money and seems to have a "pay me to fix bugs" attitude. This breathless "omg must donate now" sentiment dominant here is highly questionable.
gpg should be under and funded by FSFE not via begdonations and german government funding.
There's nothing wrong with that attitude. There's no reason why he should be doing work without pay.
If people send him bug fixes and he refuses to merge them, that's something else. But he doesn't have to work for nothing. I assume that whatever money he may be receiving from the German government may be used for other kinds of developments, not bugs that don't affect him.