As of December 16'th, 2016 fedora has started to support only Kerberos credentials, they have even removed the SSL setup from /etc/koji.conf in koji version 1.10. Does koji plan on continuing support for both security systems?
We are a small company with 12 developers creating packages for Fedora, RedHat, and Centos and currently use koji with external repo's to package our product. Switching to a Kerberos security system would be difficult and time consuming. Hopefully, koji will continue to support SSL.