This feels like too literal a translation. I think it would be more natural to say "Emilian is not wicked". Or am I missing some nuance?
Seems correct. It's a very common pattern in many languages that you possess a property rather than are a property. It could even differ according to which property you're talking about. In English for example, it's perfectly natural to say that you "have great courage" when you want to say that you are courageous, and in German you would "have hunger" when you're hungry. But for other properties, like for example colour, it would be unnatural. You would never say that a car "has redness", but the car "is red".
A free translation: There's nothing bad about Emilian. Of course, this departs way too much from the original Swahili to be accepted by DL. "Ubaya" can mean wickedness/evil, but it can have a milder meaning in many contexts. Ubaya wa ofisi yetu, (ni kwamba) watu wanagombana kila siku.
Their "correct" answer is very bad English. But perhaps it is hard for a computer algorithm to make it more idiomatic.