Ted Kaehler has done two implementations of DBJr AFAIK, one in Squeak and one in Javascript.
Here's the javascript version (for Lively Kernel)
I had to dig to find the Moshi image, but here's an actual Squeak image -- and I think this was the right image -- note that this was a prototype and that some things (e.g. saving) aren't implemented. Also, I can't get it to open anymore, but I think that might be because I don't have a non-Cog VM now? Not sure which .sources file you want but I'm betting it's V3. The file of interest is "Text Field for LObject.zip"
I was really fascinated with both the approach and the presentation he did here. Active essays are cool.
Meantime I have to figure out why I can't open the image. I thought Cog could open older images, but interpreters can't open Cog images. Hmmm.