By default, most thumbnails are replaced with random screenshots to try to let you get a sense of what the video is like. This can be changed in the settings to show the original thumbnails instead of you prefer them.

All the crowdsourced data is public and under a creative commons license (https://sponsor.ajay.app/database). The code is also fully open source under the GPL. The magic of open source is that anyone can continue the project or fork it to their own desire.