About Ekattor School Management System

Hello, I have found a school management system source code on some website, its interface is mostly different from ekattor school management system, it is a customized version of ekattor software, I think. and it is there free to download as php open source. So my question is, what is your policy about those customized source codes availble online for commercial purpose usage? Can I use those source code to sell to my client ?