Aaron
That is an interesting question which I have not thought about before. I took a look through the documentation and find it generally described as the image file but without a particular name. I looked at the software download page and it does not have a particular name there either.
I guess the different approach to naming the OS (or not naming) reflects the fact that Cisco purchased this technology from another company and so the naming convention would be different from products which were actually originally developed by Cisco.
HTH
Rick
HTH
Rick