Maybe the relevant section is left over from the previous license, which was CC-BY-NC (http://blog.mapillary.com/update/2014/03/17/mapillary-goes-c...). Alternatively, IANAL but I imagine that the individual photos could still be CC-BY-SA (if, e.g., someone else redistributes them) but that the service itself cannot be used for commercial purposes. As bulk exports are prohibited (2.1) and dumps are not provided, however, this would mean that the data is CC-BY-SA in theory but hard to reuse commercially except for individual pictures.