most people that uses open source scripts intend to scam people, can you tell us why you want such scripts? most exchange sites have their own dev team to develop and grow, if you only plan to use open source scripts then it will be very hard for you to gain people's trust on their money to use your exchange. if you don't have a capital to start with it is better to ask few friends to invest in your plan, hire a professional dev team to help you create unique exchange site, after that some people might use your site