Its more then that... It's not even inmutable, not really. There are some things, like privaCy of access, that can be mutated by manipulating Java class objects.

That said, maybe the difference here is how often the janky metaprogramming of classes interferes with day to day peogramming; a java programmer might have never seen this stuff, moreso then a ruby one?

Yeah, the correction re: prototype inheritance is a good one.

That said, there is a qualitative difference in what we call 'classes' in those two environments, which is part of why I think there's confusion. Class in Java is a fairly different concept than a Class in Smalltalk, Ruby, or JS.