Yes, it has been, from my metrics at least - with predictable results! (Seems to be a phased/tranched rollout.)
Don't get CloudFlare to budge you to another IP, you'll never know what may or may not be listed - most of the content on the default filter is not porn. This is Sky's problem, not CloudFlare's.
It's deplorable, but entirely predictable (and they were repeatedly and loudly warned!) that innocent bystander sites have been blocked by the censorship on Sky's broadband network that people haven't even asked for.
Have you perhaps considered legal action against Sky?
You may also want to let them know, but they can't admin the filter themselves (last I heard), so can't whitelist you, and the equipment they have cannot proxy the site on their list without also affecting yours. (That you share an IPv4 address is not itself an issue with CloudFlare.)
Don't mind me, I'm just getting snacks. This is going to get worse.
> Have you perhaps considered legal action against Sky?
This is the real, correct solution but seems unlikely. The OP said his client is unable to shell out the extra $20/month for SSL on Heroku so it seems unlikely they'll want to pay for lawyers required for legal action :(
It asks you when you first connect the router. I suspect most people you have contacted are likely to have subconciously (or thoughtlessly) opted in.
If you let me know the URL, I can test from here as I'm on the end of a Sky connection without the opt in blocking so that would confirm if it is that or not.
A lot of people get technicians in to install the hardware, their default mode is to just next,next finish until the router is ready. Chances are it's the technicians themselves turning on the blocking. Not in a malicious or tinfoil hat way, just out of a desire to get the job done quickly
This is opt-in so they clicked a button somewhere when Sky asked them if they wanted adult content blocking.
If anyone opts in to blocking; it's their funeral. It doesn't work. Sky's blocking even kills ThinkPad wiki.