Way back in 1999, when I was in high school, I started my own embedded GUI project for a little 68EZ328-based Linux machine I wire-wrapped. This turned into PicoGUI, which I spent about 4 years working on. It was a great learning experience, but I eventually stopped maintaining PicoGUI. (I wrote a short document at the time, explaining why.)
Apparently there’s at least one device that still runs it… the mvBlueLYNX networked camera from MATRIX VISION. The manual has a whole section on PicoGUI, including a link to some Doxygen’ed docs for the client library, configuration options for pgserver, and so on.
Looks like they’re using PicoGUI’s “Classique” (Classic Mac OS) theme 🙂