I think lsd5you is probably referring to the fact that you can trivially build classes on top of prototypes, while the reverse is not generally true (as far as I know). So a prototype-based language can easily express both classes and other forms of OO.

Sorry, but it isn't that hard to build prototypes on top of classes in a dynamic language. The cleverest and shortest implementation I've seen is http://snippets.dzone.com/posts/show/3378 where the following snippet of Ruby code does it:

  Proto = Class.new(Class)    # Beware: magic.
  def Proto.clone
    Class.new(self)
  end

(Follow the link for an explanation of usage.)

However several other languages have implementations. For a random example see http://search.cpan.org/~teverett/Class-Prototyped-1.11/lib/C....

Yeah, although the trade off is that as class construction is procedural with prototypes you know longer have a declarative type system. Any type checking will have to come from type inference (when possible).