If anything it would be the internet hate machine (http://knowyourmeme.com/memes/internet-hate-machine), but I don't see 4Chan mentioned. I doubt they'd participate in dDOSing a Tor provider, not your personal army and all that.
Before you have to read the whole article: even though the title suggests otherwise, the attack is not related to 4chan, but rather a "rival VPN service" as suspected by one TorGuard administrator. (TorGuard was the attacked website, a VPN provider)
Umm... errr... the 4chan Party Van is the FBI. Back in The Day, 4chan had basically only one real rule -no child pornography- and the people running the site were extremely conscientious about cooperating with law enforcement when people broke that rule. I assume they still are: it's just there there are more rules now, though most aren't the sort that will incur the wrath of the FBI when you break them.
The harassment described in the article also occurs, of course, but that's not the party van. It's more like what they'd call a raid.
So nothing they did actually worked before shelling out to cloudflare? Nice advertisement but now I hate the author for misleading me that the article contains anything instructive.
If CloudFlare think they can stop 4chan from griefing them, they have another thing coming, I think. Calling out 4chan like this is like drawing a picture of Muhammad: just don't!
http://knowyourmeme.com/memes/4chan-party-van