Peter's page has a lot more than history. The main characteristic I notice about it is that he has such an extensive collection of formulas with tau replacing pi. But I certainly agree that he's the history expert/buff in the group.
Prior to August 17, Peter's page was titled "Gregory's constant τ" to honor the 17th/18th century mathematician David Gregory, who was thought to be the earliest known person to seem to recognize that circumference/radius was the important number. Back when other people were using "π/δ" to signify "perimeter/diameter", he used "π/ρ" to signify "perimeter/radius". But in early August, I was reading Wikipedia's page about "Approximations of pi". They list major historical calculations of pi, and I noticed it said that in the 15th century, al-Kashi calculated 2pi, not pi. I figured that might be a sign that he used 2pi in the rest of his work too. But I'm not a history buff, so I just sent an email around letting people know I'd come across this. Peter dug into it and found that indeed, al-Kashi had used circumference/radius in his work. (I don't know what symbol(s) he actually used.) So since al-Kashi was first, Peter transferred the honor to him. Gregory's constant became al-Kashi's constant. But I guess Peter hasn't gotten around to changing all the places on his web page where he uses the term.
Yeah, I find the different forms of al-Kashi's name strange too. His full name is quite long, so they shorten it, but use only the portion that tells what city he's from, Kashan. Maybe al-Kashi and al-Kashani are like Delawarean and Delawarite?
Earlier this year, I see Peter worked to prepare/soften the ground at Wikipedia. The math mavens there have been very dismissive of the whole tau idea. They really resisted introducing the topic, so from what I can see, Peter found ways to highlight the importance of 2pi, without actually calling it tau, which they wouldn't have tolerated. It's actually pretty funny when I'll be reading a Wikipedia page on a related topic and come across one of these entries. I'll think, hey, that really clearly points out the importance of 2pi. Then I'll get suspicious, look at the revision history, and sure enough, Peter wrote it.