I think, it needs a discussion.
- have built-in-to-some-languages solutions excluded
- but Golfsript code is in fact a couple of built-in functions, and more: they are shaped for codegolf!
- not be optimized for one language or one class of languages
- what about reverse: language optimized for a task?
- The language you use should not be invented just for solving this code golf.
I can't find a question on SO, which I read a month ago, but it was about, for what is the Godegolf at all. The main, which I remember from answers and with which I fully agree is that "Golfing helps us to know our language (which we, programmers/coders/SO-audience, need for profession) better, to find new methods/functions, to increase our useful proffesional potential".
I think, that Golfscript is unuseful, and it's not a language at all. It's a kind of Ruby library (proof - http://www.golfscript.com/golfscript/golfscript.rb), and its main and the only purpose is to cheat in Codegolf. Nobody would use it, if Codegolf dissapear.
I suggest to oficially never to count it as a winner.