I just looked into this more. The September 10 date (and the URL
above) is from a similar action that happened in 2014. I did find a
page for this year's action https://www.battleforthenet.com/july12/

... but it's not linked to yet from the main page, and it says:
"you’ll embed a bit of javascript in the header of your site. We’ll be
sharing the code for them soon!"

So I think maybe it's too soon for this. Let's check back next week.