SevenDos, could you look up your protection history and let me know the specific file name that was classified as a Trojan? If it wasn’t the installer or the executable, I’d submit that to examination and potentially whitelisting, too.
Concerning the Steam version, it’s self-contained, but if you log in using your username and password you have here, apart from unlocking a pack for free, you also link your accounts, so if you unlock/buy any packs on the website, they’ll also be added to your Steam account and you can use them there, too. If you are paying $ the prices are identical on our site and on Steam, the only difference is Steam takes an additional 30% cut, so if you like the software and want to support it being developed forward you could better support us by purchasing from us directly. But it’s really up to you, no difference in the content & features delivered in the end. 🙂