No, Inkbox is not henna.
Inkbox is different from henna with regard to the plant used, its color, and in its application process. Firstly, Henna is derived from the Lawsonia Inermis plant, whereas Inbox is made from the Genipa Americana plant.
Natural henna is a dark brown paste, and the stain appears orange when the paste is first removed from the skin. This darkens over the next couple of days to a deep reddish brown. Inbox's ink is a navy blue when first applied, but in a period of about 36-48 hours the ink will darken to an eventual dark bluish black. Traditional henna is applied directly to the skin through a cone tube. A mixture of lemon juice and white sugar is then applied over the design to remoisten the henna mud so that the henna will stain darker. It is left on the skin for 2-6 hours and develops over the next 1-3 days Inbox's Freehand Ink is applied directly to the skin using their ergonomic bottle and stainless steel tip. After one hour, the formula is rinsed off with soap and warm water. The color gradually darkens through oxidation over 24-36 hours.