gutenberg.org has a link to view it in German on the front page. I guess if you provide several translations and use a top level domain like .org, you are more likely an international web site than an English-only .us web site.
That's not to mention the countless expats/second language speakers around the world.
Having a German language version of your website/product is by no means equivalent to being subject to the jurisdiction of Germany the country.
Never said that.
That doesn't make them subject to the laws of every country. Most legal systems do not accept the standard the German court used and require a more significant physical, legal or economic connection to a country before a website may be subject to its laws.
PGLAF appears to be complying because it wants to win an appeal in German court, which might be compromised by ignoring the ruling of a lower German court. If PGLAF decided to ignore the ruling, there would likely be no consequences.