Seems like you're invested up to the point when you're wrong, which is a pattern I've observed on this site in general.
Incidentally, your anecdotal "feelings" about whether something feels original or not make for a pretty weak argument.
When you finalize a logo, you typically run a quick due diligence (a Google search) to see if you reinvented a wheel. If you did, you scrape it and start afresh. Tox didn't do that and they should've.
If they came up with it independently(a very legitimate question given the similarity of the --- very nice by the way --- logo, but one they seem to have evidence for) then there seems to be no moral problem or even a legal issue.
You're basically claiming "I thought of it first, there for it's mine" which is both legally wrong in the US for copyright(independent creation is a defense) and morally bullshit in the same way that Amazon's one click ordering patent is.
I am not claiming this, this is how things work in the logo design industry. There are of course copyrights, trademarks and legal matters, but there are also professional ethics. Ideas and concepts are getting recreated all the time, that's life. But it's also why people post sketches and ask if anyone has seen anything similar, only to discard them and move to another concept.
As such, why not just leave the logo of Tox in peace? Especially since it's a FOSS project with noble goals (even if they have yet to reach those goals, which is not surprising considering how early in the development the entire project is) and not some commercial entity intending to profit off of it.
I have plans for it. It wasn't just an idle doodle.
In this case, the products/ideas are straight-up competitors.
Oh wait
This isn't competition. It's complaining on a professional level.