One piece of feedback: Could you add some explanation (for humans) what we're supposed to do and what is happening when met by that page?
I know there is a loading animation widget thingy, but the first time I saw that page (some weeks ago at the Gnome issue tracker), it was proof-of-work'ing for like 20 seconds, and I wasn't sure what was going on, I initially thought I got blocked or that the captcha failed to load.
Of course, now I understand what it is, but I'm not sure it's 100% clear when you just see the "checking if you're a bot" page in isolation.