The main reason it is on the website, as opposed to my blog, is because I am making extensive use of Rails as the world's most over-engineered templating system to write that. It wouldn't be interesting at all without the cart to play with, now would it? I'm all about avoiding sucky user experiences and "I am going to extensively discuss a feature of another website. Please open that website in a tab and follow along" is a sucky user experience.

But yeah, to the extent that people find this article as valuable and link to it, Google will see my site as more trustworthy and send me more frazzled teachers trying to get ready for fourth period.

I really don't have a problem with that: they get their prep work done, I get money, the rest of the world gets a few hours of engineer time writing what I hope was a useful article as a result of the cross-subsidy. The notion is quite similar to OSS. Its a win for everybody.