Is there anything unique about producing a hash from an image or is hashing tech effectively open source now? I assume the latter.

Is there any way to get ahold of their list so it can be duplicated?

I'm not buying that the mere generation of a hash from an image creates a copyright or anything else proprietary re the hash, unless there's something really unique about how the hashes are being generated, i.e. the result for each "work" would have to uniquely transform into a new and unique work, and not merely a derivative work.

This copyright angle is only one possible attack, and only works assuming the list can be acquired and duplicated without "permission."