On the site it says:
Hierbei handelt es sich nicht um die originalen Versionen von osticket.com, sondern um modifizierte, übersetzte Versionen.
In English it means:
These are not the original versions from osticket.com, instead it's a modified, translated (to German) version.
So based on that it's clearly stated that it's NOT an official osticket and I wouldn't use it even though support is offered and it's in German, which is usually great for a German guy like me, but since we only use OS and software in English at my company I prefer the original osticket and always confused with German OS or software (even at private devices like my phone from which I type now)