I planned to go into more detail in JavaScript since it's probably the most widely used prototype based language. But the article was getting long so I left the brief mention and maybe revisit it later to compare how the limitations of only one immutable prototype slot affect usage. It's one of the reasons I left doing the examples 'as an exercise for the reader' to see how other people approach the examples given before I gave my approach.
probably the most widely used prototype based language
Not probably. It's arguably the most used programming language, period.
That being said, I'm kind of glad that you didn't go into much detail about it. There's a lot of Javascript info online, and I'm more curious about the other languages you tackled. It'll be interesting to see if there are any responses that focus on applying some of the benefits of other prototype languages to Javascript development.
It doesn't mention Lua, either, and Lua is used a lot in e.g. the game industry. It does mention Javascript, albeit as an afterthought.
Also, Slate: (http://slatelanguage.org/) (Never used it, though.)
I'm glad to see mainstream interest in prototype-based OO building.