Hydrogen is moving past it's bad reputation. With the push to try to move the US to a Hydrogen based economy, the PR push is starting to inform the people that gasoline is more volatile that hydrogen.
Let's leave the Hydrogen discussion now. We know they're using Helium and that there's been no confirmed word, only speculation in the Scientific American article about the use of Helium. For all we know, they've allowed for off-gasing of helium so that they can just service the craft normally without having to worry about gas leakage.
-Dan