Have you looked at crashplan? Although I can't say I've tried running it on FreeBSD...
A quick Google search gives me the feeling that it runs under FreeBSD's Linux emulation and the port seems to break occasionally. I could run it on a real Linux in a VM on FreeBSD though, so that's a potential option.
(Disclosure: I'm a paying customer of CrashPlan, but otherwise have no connection with the service.)