You don't litigate the GPL in court as such. You litigate a copyright violation. Christoph is going to go to the judge and say the German equivalent of "your honor, VMWare is distributing my copyrighted work without permission. Make it stop please." VMWare then has two choices: either it says "but we have permission, a license to do so" whereupon it needs to obey the terms said license, or it needs to immediately cease distributing Christoph's copyrighted work.