The Wikipedia article on the X Window System is on the front page on September 3rd. Knowledgeable geeks (with their references to hand) are invited to help tart it up as needed.
The difference between X.org and the remains of XFree86 was never more apparent than when I was trying to get the article to featured status in January. I sent the same message to both projects. X.org responded quite helpfully, both on-list and privately. XFree86 reacted like ... erm, this: [1] [2] [3] [4] [5] [6]. That was the entire public response, and also the most lucid response — I also got private messages saying things like I should be careful who I choose as friends. Like, what the fuck. X.Org is the project that's alive and well; XFree86 is somewhere past "dead project" into "undead zombie project, dropping green radioactive bits on the pavement."
Me: Hi, I'm writing about X and want to get it right. Can you help?
X.Org: Sure! (info)
Me: Thanks!
XFree86: YOU! YOU'VE BEEN TALKING TO THEM, HAVEN'T YOU! YOU'RE CONSPIRING WITH THEM! THOSE GUYS! THEY STOLE IT ALL! THEY PUT A RADIO IN MY HEAD! LINUX/BSD WEENIES! I'LL SHOW 'EM! HELL YES!
Me: Er, thanks. (wipes spittle off)
Also: if there's someone who thinks they could describe how X actually works in detail off the top of their head, the spinoff article X Window System protocols and architecture is a pile of fragments and needs to be more or less tripled in size and given a structure.
Update: The Cautionary Tale of XFree86 describes how almost all XFree86 contributors basically just got up and left one day. Wheeler attributes this to the GPL-incompatible license change, but I think that was just the last straw.