Which is not referenced from the linked article. What is the point of posting something with all but no information?
They should have submitted http://sel4.systems/ as the link, instead of the github link.
I'm not sure who submitted the link (I don't think it was anyone from the seL4 team), but I inserted the http://sel4.systems/ link into the repo's README file, which will hopefully help a little.
Oh, I didn't realise the linked article wasn't the actual seL4 website.