One of the co-authors here. Never expected this to end up on HN! For people interested in quatum computing and open source tools, we're also organizing a quantum computing track at FOSDEM19 (February, Brussels) [1].
The correct IP to, i.e. put into /etc/hosts as an workaround is: 169.55.161.194
EDIT: Actually, I might have fixed it. Let me know if you still can't access the website.
FOSDEM [1] is open to all (there is no registration or fees) - and several thousands of people come every year.