Sadly, it was a short lived project :-(
From the Chart.js homepage :
"At midnight on the 18th March 2013 I posted Chart.js online. On the morning of the 19th March, I've had to take it down due to IP concerns with my current employer."
Hah, looks like they changed their mind already, the project is back online, and that's great news as it is a really promising library.
I will most likely use it for my next project.