The argument of "the GPL has not been tested in court" is a myth in the open source and free software world. It's not been tested because no one has been dumb enough to try it, at least in the US.
Copyleft is protected by the established laws of copyright as copyleft is nothing more than copyright flipped on itself ("i transfer my copyright to everyone with the only requirement that everyone transfer their copyright to everyone else when distributing."). Anyone trying to disprove the GPL in a court of law would have to effectively disprove copyright. That would effectively undermine their own argument.
Check out Eben Moglen's work for a more complete discussion.
I don't know about Germany. If, as Malte says, that GPL3 will address this, I hope we will move to that when it finally comes out.
talli
