Lucent had little to do with Inferno externally
after 1 September 1999, and nothing to do with
it externally (technically) after 1 March 2000, so there was
no reason for Lucent to keep that external domain name.
Internally Inferno continued in use in Lucent in
several projects (both products and research),
but even control of the trademarks had been transferred.

I've no idea why the current owners of that domain name bother
to keep it registered. Perhaps there's a little back story there;
I don't know.