Yeah this is a complete bait and switch scam. It comes off as a "free extension" but when you download it they straight up are like "give me money or we'll lock the extension and also cause physical damage to your computer with a "memory leak" issue." Most of the "5 star reviews" are obvious AI bot reviews too, so don't let that fool you either. I mean sure the saying its "FOSS" but requiring payment is one thing and yeah you should just say "we require payment" on the ad. Purposely wording things in a way that beats around the bush is scummy, but a lot of these extensions and apps do this and it's expected at this point unfortunately.

Having "memory leak issues" due to faulty programming which causes physical damage to someone's computer, and to also require payment at the same time makes me feel sorry for the unfortunate people that are less computer literate that actually paid these hacks $10 and are wondering why their CPU and Memory are running at max load constantly. Use that $10 or whatever the exchange rate for your country is and go to the local corner-store and get a cheap pair of sunglasses if you need dark mode this badly. It's safer for your computer, phone, and wallet. We're in a memory shortage crisis as is and these jerks are going to cause you to be paying more than $10 for their badly programmed "gimmick" down the line.