Before answering this question, I need to understand what you mean by the word “clone”. The clone scripts presented by all reputed web development companies are absolutely not copies of any website. It only resembles the important features. A Facebook clone is not a copy of Facebook. It is a social networking script. Web development companies use this terminology to make it easy for the buyers to comprehend. The purpose is to explain how it works. It is the primary means of communicating to your potential customers what the software is about and how to do stuff with it. If you’re buying a clone script from any web development company, it is definitely not illegal. However, copying images or data from any third-party website without permission is completely illegal.