This is an important issue, but the WSJ is a mainstream paper. This article doesn't go into an in-depth discussion of the technical issues, and it also assumes very little familiarity with the nature of Chinese Net Censorship (which is rather more complicated than the "Thought Police"/1984 picture painted here).

Here's one good link which discusses the Green Dam programme in more detail: http://sun-zoo.com/chinageeks/2009/06/15/ai-weiwei-all-thats...

Edit: Actually, I don't think that's the article I had in mind (it came up on RSS a few weeks ago). But it was from that blog, which has several good discussions about this topic.