Ask HN: How does Forbes get around the "first page free" rule in Google?

I need to amend a tax return and, today while searching in Google for something [0], I clicked the first result which was a Forbes.com link. I was immediately taken to an ad with a "Continue to this site" link. How do they do that? I thought this was not acceptable according to Google [1] but Forbes has been doing this for months.

[0] https://www.google.com/search?q=rules+to+follow+when+amending+tax+return&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

[1] https://support.google.com/webmasters/answer/74536?hl=en