This recipe calls for either raw cacao or cocoa powder. Both are fermented foods. Cacao is made by cold pressing unroasted cocoa beans. This process keeps the living enzymes in the cocoa and removes the fat. Cocoa powder is raw cacao that's been roasted at a higher temperature. The extra sugar in this recipe is food for the kombucha and will be consumed by the end of fermentation.
Make sure you use good bottles made for brewing. Check your bottles often by opening them so they don't explode.