What is Open-source diffusion model in prestashop?

Question

I am new to prestashop and by seeing prestashop about us page there they mentioned prestasop is based upon a open-source diffusion model. what it means?

PrestaShop Software PrestaShop SA editor of the e-commerce software PrestaShop offers to merchants, through its solution, a complete platform with the best tools to manage their e-commerce on a daily basis. PrestaShop is a complete, progressive and easily adaptable solution for online sale. PrestaShop is based upon an Open-source diffusion model to enable each one of you to modify the software to your convenience .The PrestaShop solution often enriches with new features and partner services. The PrestaShop solution, satisfies more than 50,000 merchants around the world, is free to download on the website PrestaShop.com, property of PrestaShop SA.

Thanks in advance

Answer 1

Your question is very general but this should answer it: http://www.prestashop.com/en/osl-license