In my opinion the layout of a blogging website falls more in the realm of fashion than intellectual property.
Some real intellectual property here is Rails itself which thankfully is open.
Personally, I think the design is ugly and hard to use. The OP (of Obtvse thread) should get a designer and make some much needed changes.
Edit: Downvoters - is it because I said design is hard work, or because I said I thought the design was ugly?
For example, bitbucket copied githubs design for the most part, but people still use github because there is so much more to their product. BB can copy them all they want, but github will have the users and will be considered good design while BB gets called a 'clone'.
If you make a blog platform, which is simple to clone, just open source it and move on. This is a case where imitation should be flattery. Bask in the glory of knowing the world is switching from wordpress to your platform.
(theres also longterm revenue possibilities in that case for a savvy businessmen)
Dustin's initial response to this (which he edited later) and his general attitude might have contributed to my opinion.