I don't think he's passing judgment, saying that Cocoa is too closely coupled, I think he's just comparing why it works better with Objective-C than with Ruby. Amongst other interesting projects are Nu, a Lisp designed for Cocoa and Objective-C; and MacRuby, a fork of Ruby that uses Objective-C's runtime and garbage collector, and language tweaks for named arguments.

http://programming.nu/

http://www.macruby.org/