Thanks very much for this! I've written a lot of stuff on there (I'm the Patrick Stevens whose name is splatted all over the screenshot). I asked them a year ago (ish) whether I could have a data dump, and they said it was Too Difficult; and I didn't bother scraping it myself. I'm glad you actually went and did something about it!
Nice project thanks. It's also consistent with my analysis that Arbital's fancy wiki features never added much value (say, more than +30%) beyond the value that that content would have if published in a pre-existing format and venue.
Update: Arbital Scrape V2
I've scraped http://arbital.com as the site is unusably slow and hard to search for me.
The scrape is locally browsable and plain HTML save for MathJax.
https://drive.google.com/open?id=1b7dKhOzfMpFwngAeI8efeOzv147Lv_mx
https://emma-borhanian.github.io/arbital-scrape/
If there's interest let me know as I may tidy up and open source my code. edit: working on this
Mirror: www.obormot.net/arbital