What about referencing the code that is not officially published

Let's say I go to someone's website, look up the source and use some of the JavaScript idea/pattern/code that is not a part of the wider framerwork/something similar, but a unique code that was written by the author of the website.

If it's not officially published in e.g. some coding tutorial, but I looked up the source of the website, is it appropriate to reference directly to the code on that website? (e.g. http://ift.tt/18glala)

Small edit #1: Just to mention, I have extensively edited the script, it is still similar, but not the same. It is about 100% longer, but there are similarities.