Hello,
After reading the docs I have a few things to add:
1. we could use that software, but I would rather build something from zero. The resulting site will be easier to maintain and a LOT faster. Plus if you will need product feeds (From vendors), it will be a lot cheaper to implement than with any other software.
2. I made my own affiliate system a few years ago. I can remake it for PHP5 and it has many advantages: I can vouch for it's security, and I can make cookies that only Eraser can delete:), by utilizing a plethora of cookie technology like cookies, local storage,web storage, databases, computer tracking etc (if you want that). Or I can use that one, but the affiliate system will be much better integrated into the site this way. Yes, that one is ready, but it still requires massive integration into your own admin panel (or Shopy's admin panel).
The other requirements are OK, multilanguage is no problem and as a security expert, my solution will be secure and the site will be fast (I can use Redis, Memcache, avery optimized mySQL structure and fast and simple PHP code).