I have the Adafruit DVI board and have been hacking on it some. It's more fun than should be allowed.
There's a project to get this running using Rust[1]. Currently it outputs the blue channel with sync, but has trouble with the other two channels. I don't have a hardware lab with scope, logic analyzer, etc., so it's not easy for me to debug.
In the meantime, I've been doing some experiments in the C codebase as well[2], mostly in the direction of proportionally spaced bitmap text, using the fonts in the X11 distribution.