Versus literally means "green juice" in French (I know there's a "te" in French, but it's not pronounced).
Verjus is a highly acidic juice made by pressing unripe grapes, crab-apples or other sour fruit.
So versus is sour juice, nothing more, and we should treat it like so in our research for food safety.
If grape juice develops an off odor, flavor or appearance, or if mold appears, it should be discarded.
Pretty vague, but I stumbled upon this article from The Bulletin
Moldy or fermented juice is not particularly dangerous to drink, said pediatrician Dr. Kathleen Berchelmann of St. Louis Children’s Hospital. One concerned parent recently took a Juicy Juice box filled with mold to the St. Louis hospital; the juice was not past its expiration date, and the child who drank it had no symptoms.
There's more context in the link above that backs up how mold in juices might not be that dangerous.
Also, from Childrens MD:
If even a tiny bit of air gets into the container molds can grow. The good news for my patient is that moldy, fermented juice is usually not very dangerous to drink.
Though symptoms are possible, from Rainbow International:
But luckily, swallowing a few sips or bites of a moldy item typically isn't a big deal thanks to stomach acid, which is strong enough to kill most pathogens. Some may notice transient GI upset – nausea, cramping, and diarrhea - but most who've imbibed a moldy mélange will notice nothing.