"This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License.
This means you're free to copy and share these comics (but not to sell them)"
As posted on xkcd. Sure, this page might be a 'ripoff' in a general sense, but everything is exactly the same, and they're not violating the terms of the license. Not that I approve, if this is not condoned by Randall, it's just that there isn't much of a reason to get your panties in a twist.