Open source projects can be sponsored, and it's perfectly fine to list sponsors at the bottom of the settings page. I'm not sure what kind of advertisements and data harvesting tool are you seeing, but anyone can indeed verify that you're making stuff up by going to GitHub.

This is the commit that lists the logo of sponsors on the options page of the extension:

https://github.com/dessant/search-by-image/commit/b8de70371695f8f1fa8069d2edbfaa4c7b705dc8

It's a local image, with a link to the website of a sponsor.

Please don't spread false information about my projects, I have never collected any kind of personal data. I have reported your review to Mozilla.