The fee is only for their benchmarking software, whose results get uploaded to the website.
only a limited unspecified number of users can test for free at any one time, and if no slots are open, then only subscribers to the $10-per-year Pro plan can test
When there are free slots, users will have to complete a 3D captcha minigame where the goal is to shoot down 13 ships. The minigame isn’t particularly difficult on the surface, but it can get very tedious as there are very few opportunities for users to actually shoot down any ships. We attempted to complete the captcha ourselves but gave up after a few minutes