DocumentCloud self-installation instructions have been removed. They were out of date and required enormous handholding.
We understand the desire to self-install and we're considering how best to support that. But until then, we think it's best to call it an officially unsupported task not for the faint of heart, rather than imply support but offer only broken instructions.
If you really want to give it a go, you can view this file history on GitHub to see the old instructions, but be prepared to hack through some underbrush.