Whether or not you "strongly disagree" doesn't change the fact that it was created independently by other people as well, evidenced by the third comment in one of the links latitude posted (http://logopond.com/gallery/detail/165288) and in archived threads where multiple people came to the current design on 4chan's /gd/ that Daiz posted.
As I said in the (edit) of the original comment, the originality is secondary to the timing.
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.
Except, you run that check to make sure your not running afoul of someone's trademark restrictions/ using a logo associated with an existing brand. (Which, unless I am missing something here, they are not.). They should have run it, but just because they found your result doesn't mean they had to scrap something they (allegedly) did themselves.
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.
You don't actually seem to be using the logo anywhere, though. On your site you write that "I had (have) plans to write an Instant Messenger client with proper support for privacy. This was the logo concept for the project"[1], but this project does not actually seem to exist (at least not in any public manner).
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'm not invested in this issue enough to argue about it. I look at a lot of systems like this and was struck by the novelty of the logo, is why I commented. Take that for whatever you think it's worth.
If you extrapolate my comment into points I wasn't trying to make, I think you'll find those arguments very easy to tear down. If that's a productive exercise for you, be my guest.
I strongly disagreed that the concept was't unique and original. I'm clarifying though, not trying to give you flak; like I said, I don't much care about this leg of the thread.