This isn't obvious at all, but you need to create an account with them (you only need an email address). Then, in your account page, you scroll down and there

This isn't obvious at all, but you need to create an account with them (you only need an email address). Then, in your account page, you scroll down and there are instructions for installing/running fakebox (and others). The "demo" is actually a docker app that spins up a web application of some sort. I'm firing it up as I type this, and I'll checking it out soon-ish.