Fedora and CentOS are supported.
Ubuntu has just been making some changes and that is why you see all the chatter about Ubuntu lately.
I would NOT update to 14.04. I, personally, wouldn’t upgrade form 10.04 ever, I still have servers running 10.04 and I have NO ubuntu issues at all! Fog works wonderfully on a GOOD base OS. 12.04 would not be a bad upgrade, and 13.10 would be safe too.
Personally I would back up my databases and move my fog folders and install 1.0.1 on the 10.04 machine.
If you would like to upgrade your Ubuntu I would upgrade to 13.04 or 13.10.
It would be recommended to upgrade to OS BEFORE installing FOG though.