To start using and working as a SaaS version of React App Builder you have to do few steps.
Open the source code you got from CodeCanyon and in Builder/src/config folder find app.js.
By default option for using SaaS version is set to false.
Find defaultExport.isSaaS and set to true
defaultExport.isSaaS = true;
Find allowRegistration and set to true
Next: Integrate payments