Epigraver is a macOS screensaver that executes user defined command line programs and displays the textual output from them on the screen.
The transition from one output to the next is animated using various animations. The background color, foreground color and used font can be configured. And there is a whole scheduling system that enables setting what command line program is used when in what circumstances.
The screensaver is open source and available on its GitHub project.
Why and how I came to develop a screensaver is described in a blog post.