The answer is here – https://www.nextscripts.com/faq/#q5 or here – https://www.nextscripts.com/software-license-agreement-pro-plugins-and-apis-terms-of-use/
Question: I am running a number of blogs and I’d like to use your “Pro” plugin on them. Do I need to buy a “Pro” license for each one of them?
Answer: Our licenses are issued on a “Per User” basis. It means you can use one license on all your sites, but you can’t give it to other people. You can use Plugin and API libraries on all your sites/blogs, the only requirement is that all those sites/blogs must be yours. You can’t resell or re-distribute the “Pro” Plugin and API libraries or websites with per-installed “Pro” Plugin and API libraries, and also you can’t install plugin and API libraries for your clients. If you would like to install SNAP to your clients, you need to purchase a separate license for each one of them.
If you are interested in reselling plugin or would like to install it for your clients you can look at our affiliate program (https://www.nextscripts.com/affiliates/) or developers/resell packages: (https://www.nextscripts.com/developer-and-resale-licenses/)