I recognize that in the background that the JAMF Netsus is using Reposado and there is probably a manual way to update Reposado to pull in Software Update Catalogs for 10.11, but in my mind JAMF should just be releasing an update for the appliance to support it. Any ETA on this?
Check out the release history and commit history.... Not much activity, last release November 2014
Pretty sure that NetSUS is not an actively supported product, but is a community driven product.
So in short just run Reposado for updates and bsdpy for netboot and you'll have a much better time.