They have changed the server that it is hosted on. The old server just carries the "we're moving" message.
The reason that some people can see it and other can't is simply because the changes to the DNS entry for the server haven't propogated everywhere yet. It takes a day or more for this to happen normally. Some people are being sent to the IP address for the new server, the rest are going to the old one.
My DNS server was also taking me to the old site, I did some manual DNS queries to walk from the root servers to the new server details to get the IP address that I posted. The IP address should work equally well for everyone, until the DNS entries catch up.
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Remind me to change my signature to something more interesting someday