We're all used to Germany having relatively strict rules when it comes to violence in video games, so it's not necessarily surprising that PS4 players in Germany were unable to play the Killing Floor 2 Open Beta over the weekend. However, Killing Floor 2 wasn't banned in Germany – it was rated a 18 and will go on sale as usual along with everything else.
So, what happened? Apparently, an obscure rule in Germany prohibits the release of any game rated 16 and above by the USK (Germany's ESRB) if that release is free of charge. Since developer Tripwire Interactive of course didn't charge anything for the Beta, players in Germany were unable to download it.
Although, it's interesting to note that no reports of such a restriction came about during the beta period of Call of Duty: Infinite Warfare, which was also rated an 18 by the USK.
Killing Floor 2 entered its open beta period over the weekend, showing that it's finally ready for a full release – planned for Nov. 18, 2016. It will also feature PS4 Pro Support.