It’s something we’re consistently revisiting, I came back to this after spotting it on the weekend to find a fair few detailed explanations of options here, cheers.
One issue with the captcha stuff if we were going that route is that we’d need it to align with our approach to other things (privacy at the core etc.) and it a lot of ways of doing this would introduce a dependency, something we attempt to avoid wherever possible.
Basically just that our offering should work with it disabled, it should not be a thing which is required to use Mojeek. There have been a few people who have specifically come to us, or in one case added us as default in their browser because of this (scroll down to privacy browser for dodging the preamble).