Yes, we do provide open source code. Source code for customisation is available with Developer & Enterprise edition ONLY.
Once purchased, you have access to the product full source code written in PHP and other pre-requisite languages with proper documentation and comments in code provided for other developer to fully customize & modify the script further. If you have purchased Marketer or Reseller version, the code comes protected with encryption since license is valid for single domain only.
But, once you purchase/upgrade to Developer / Enterprise edition. You get access to our open source code + full documentation with code based commented for easier adaptation by developers.