I have created a custom "users" object that I know is associated with backand's user object. However when I created them from my app using Backand's SDK, I can see the user being created in the Backand's registered users but not in my custom object "users"
It appears to be a permissions issue. Not documented well either. If your Anonymous Access is set to (read only) and you remove the try catch statement from the "Create My App User" server side javascript you will get a 401 error in your client. Set Anonymous Access to public and it works first try. There is probably a better way to do this but I am still looking into it I dont want to give the Anonymous Users that much access. But it definitely proved it is permissions issue.