There appears to be about 5000 forums using the createaforum service, I suspect that some of them have been flagged and that may reflect upon the top level domainname. The company claims to be in business over 10 years, and I suspect between ad revenue and upsell on various packages they have a revenue stream they want to protect so will try to maintain a safe web presence.
I looked at their various packages, and it seems to use your own domainname it would require their high end package which works out to $US240/year. At the moment, the free package seems to be fine.