I'd call type classes a non-OO form of polymorphism, it doesn't become OO just because you have polymorphism (if that's what you're implying). I think of OO as

I'd call type classes a non-OO form of polymorphism, it doesn't become OO just because you have polymorphism (if that's what you're implying). I think of OO as late-as possible dispatch, whereas type classes are compile time only in most implementations.