The website says "Essence is still in development." In large type at the bottom of the page.
"Thank you. I am not working on it at the moment. But I would like to return to the project when I have more free time ;)"
He's busy with something else.
Would have being nice if it in Rust. The video gave a lot nice insight to having a tabbed window based UI. It makes it more like browser. That idea can very much be adapted be used in project such as Fomos or even create a WM in Linux/FreeBSD.