I liked Objective-C anyway, so using Objective-J was no big problem, and the NS* and CG* frameworks allow for a rich user interface with a consistent and fluent look-and-feel. If you have experience developing for Macintosh or iOS, you are nearly there.
All browsers now have implemented the (“same-origin policy” (Wikipedia)). If you want to run the Cappuccino demos from disk, you need to “allow cross origin requests”, which can be enabled in Safari, Firefox, Chrome, … (web search for your preferred browser).
Cappuccino is a major open-source endeavour which relies on a wonderful & select group of developers. Learning it requires a sizeable effort, yet is highly rewarding. I thank that community for creating and continuing development of this marvelous tool:
In 2011 I had started a list here, but at ≈100 this seemed a moot effort. Just start with the first :) and the button “
Built with” will tell you. Also my vision test FrACT₁₀ is now built upon it.