I purposefully went with the approach (on my
current campaign website) that I wanted to be completely legal. Anything I've posted that is rules oriented is carefully documented. Some rules are my own, but most are not. For convienience, each subpage has a separate title as a document, and therefore has a separate copy of the OGL with a separate section 15. As I said earlier, I decided not to even mess with the d20 license itself; technically my site is OGL rather than d20 simply because of that.
And I don't have any art that I didn't make myself. Which means that (as of yet) I don't have any art. I can do some that's any much worse than some I've seen in print in some recent d20 products, but I haven't gotten around to it yet...
Other than that, I looked at the FAQ for the OGL on the Wizards website, read the OGL several times carefully, and looked at any Q&A articles on the issue, of which there are a few posted on the site. I got some feedback from some other publishers as well, who's information I was using. I was surprised to find that many of them had not done their own section 15s correctly, and I was unclear on how to proceed with my own (for example, Freeport is incorrect, and I use the Freeport firearms rules, with the proper names of the weapons changed.)
I'm not sure of a thread you're referring to, but pretty much anyone can find the information they need in the articles and interviews section of this site, the Wizards website on d20, and the text of the OGL itself.