I think you are overeating.
Let me explain why.
There can be many reasons why your antivirus will detect a threat. It could be a real threat, the website of that particular author got hacked in some way and someone inserted malicious code. It could also be a “false positive”, meaning the antivirus is set up to identify potential unknown threats and mistakenly believes some piece of code on the page is a virus or something. Many times antivirus companies will classify an unknown potential threats as “virus…” trojan…” and some numbers after that. It doesn’t mean they are actually real trojans or viruses. You can copy the name and search the antivirus software official website for more info about it.
You can find more about this from here: http://support.kaspersky.com/kav2012/tech?qid=208284682
But in both cases there was no intention from the author or envato to put your computer or your privacy at risk. This doesn’t meant it could not never happen, one should be always vigilant.