The main reason is that I have never tested it for Bangle 1 - also I'm not sure how much more work it is to maintain it for both versions. But I will definitely think mad read about it how to support both versions :)
Well, I tried it quickly on my Bangle 1, and after drawing the background it shows a "Low Memory" error and the rest of the interface is missing. I guess you'd have to reduce the size of all the icons and fonts to make it run on the Bangle 1.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
The main reason is that I have never tested it for Bangle 1 - also I'm not sure how much more work it is to maintain it for both versions. But I will definitely think mad read about it how to support both versions :)