You found e.g. Real Media Library and want to use it in multiple WordPress installations? Great that you like our work! Unfortunately, at codecanyon.net you can only purchase licenses for one domain. Therefore, you have to buy a separate license for each domain. You can learn more about the Envato Regular License in the knowledge base of codecanyon.net.
If you are an agency, for example, and have special requirements, feel free to open a support ticket at devowl.io, and we’ll be happy to help!