shopify theme uses liquid , which is a mit license, templating engine. Technically, I can fork the engine and modify it to support all shopify's tags and filters ( but for my own ecommerce platform. This way I don't have to worry about building themes or lack of them. (I am not trying to build a clone of shopify, that wouldn't be smart.)But would this be legal or any other consequences? I understand I won't be able to use theme directly made by shopify. But this will make theme development easy for other theme developers. And I will get to use their already-made themes. I don't see any reason why other theme developer would be against this idea.