I think there's a typo...

"Now let's stop here for a little bit an explain what is actually going on. In the first example the 9000:github.com:80 is actually saying forward my local port 9000 to github.com at port 80."

However at that point there is no example that uses github.com as an argument.

Edit: In fact there's possibly an issue with the ports being talked about in one of the examples too; 8000 vs 9000.