According to this thread, repository.opencastproject.org went down a few weeks ago. It has been replaced for awhile with nexus.opencast.org and I actually started to work on getting some artifacts (from ucdavis and others) into there, but hadn't made the switch in the poms. I'm moving it up into master (from kernel) and changing the URL.
Without fixing this it's going to result in slow of failed builds.
The problem is that it might make 10.6 and earlier unable to build since this was released in the kernel. We could publish a settings.xml with a mirror and maybe we should just be doing that as backward compatibility?