"if you don't take this down, google will just remove the dns, and then you lose the ability to do this in a controlled way"
Remove the DNS or start filtering by IP address. In either case, the default is using a service in a way that isn't condoned by the service provider, and that's just begging for trouble at a time not convenient to the software maintainer in the future.
If Google removed the DNS entry they'd have to reconfigure all of their own servers, too. Not very probable.
That sounds suspiciously like you're saying "I'm going to keep telling everyone to use your service because it's too expensive for you to stop me or them."
I'm not sure it says anything about the other parties involved, but your willingness to knowingly externalize costs onto others says quite a bit about you
It links to some lengthy blog post about leap seconds, which ends with:
"Google does not offer an external NTP service that advertises smeared leap seconds."
I only skipped through the blog post, though. Maybe there is a more direct rule regarding the servers somewhere.