This how they were originally handling it, before February. It would display if you visit the link from Google, or set your refer to it looks like it (this is why HN has the "web" link under articles), even if you weren't a subscriber. It's allowed, because regular users coming from Google do see the same thing as Googlebot.

WSJ have since changed that, so only subscribers can view articles, and you no longer get a "free click" coming from Google Search as Google calls it. They now show a short snippet, and are following guidelines to be labeled a “subscription” service by Google Search. This caused their rankings to drop below being a "free" news source though. But it's not nearly as bad as if they had cloaked Google.