As many of you have noticed, http://kdm-manager.com is presently unavailable.
Long story short, the company that hosts the VPS where the application lives has been under a several-days long DDOS attack. A few hours ago, a Linode engineer posted a summary of the attack so far, with a short commentary on what's going on behind the scenes to mitigate it.
In the meantime, I will be looking at redundancy strategies involving other providers, but for now, there isn't much to do but sit and wait it out.
Update: Linode's blog features a nice article on the root causes of this outage: https://blog.linode.com/2016/01/29/christmas-ddos-retrospective/