Green flesh Kiwi will not hurt your chameleons if used as a gutload for feeders. It is high in vitamin C. The calcium to phosphorous ratio is essentially balanced in the green variety. According to what I've read, it is not excessively high in goitrogens or oxalic acid.
Note however that the golden/yellow flesh type has more phosphorous than calcium, and thus should not form a significant part of the gutload.