I have the modem plugged into a router (WRT54G) but you could connect directly by internet.
However to activate the service for the first time, I had to use IE explorer as at the time NTL were using some kind of Microsoft Authentication on the back end.
I specifically remember having to power up my work laptop because I could not authenticate the modem via Linux. (Probably some Active X or whatever) when browsing to some IP address that they gave me. This may have changed or support may have given me a bum steer.
(But as they support MAC I suspect the latter now?)
Once activated, I could use whatever OS I liked. just remember if you call support later you have to speak their language
Oh yes , I activeted via some ip address URL because I told them I didnt want to install their stuff on my work laptop!