Sorry for late update, but you don't need to worry about security, because this project seems to be dead for few months :-)

DNS servers should be still working, but in very restricted mode, very few IPs are whitelisted and recursion is disabled.  It can still work if you use DNS provider which resolves Public-root domains, but your chance is slim. Last time I checked, there was only one Public-root server running, so I think that there is no point to run bitcoin domain in alternative root.  Also demand was very low, I actually received more complaints from hosting providers, than domain registrations :-)
For some reason, running idle open-recursive DNS servers with no restrictions attracts bad people, who use it to for DDOS amplification attacks against even worse people.

It was fun, but now I want to waste time and money on different projects. If someone is able to get oficial ICANN domain, it would be nice. But I'm afraid that market is very small. Non-bitcoin people will not give a fuck.