No you're not. Amazon is not the software that runs the website. 'Amazon' is the millions of relationships that Amazon has with suppliers and customers. It's the strong brand, the trust that people have that they can shop there safely, the sheer scale of the operation meaning that products are about as cheap as possible and will arrive when Amazon say they will. It's the ease of using an invisible, massively optimized chain of systems from a pretty basic app.
You can't build a new (and hopefully better) Amazon by copying the software. You need to work out how to get sellers and buyers to come to your site before they go Amazon, then build that thing so they do. How good the software is and whether it's open source of not probably doesn't matter. Better software is never going to be enough of a reason for people to switch away from Amazon.