Is it somehow related to Cat language (http://www.cat-language.com/)?

Yup, it is. From the FAQ:

"It’s also intended to be a practical successor to Cat, which was the first statically typed concatenative language."

Yeah, I hope evincarofautumn keeps chugging along with it. Last I saw I liked the ideas/philosophy behind it. Nice to see that the front page has a more interesting code example than last time I checked the website out. Readable use of matrices must be one of the biggest doubts that people in general have when it comes to what concatenative languages can pull of cleanly.