Hello @ForestArgan,
In accordance with ThemeForest’s license policy (https://themeforest.net/licenses/standard), you can use one license for one project. If all of these stores are part of the same project, then you can use one license. However, if these stores are separate projects, then you will need to purchase individual licenses for each project.
It does not matter whether you use a subdomain, main domain, root folder, or subfolder; if these sites are different projects, then you will need separate licenses for each project. If these sites are copies of the same project, then you can use one license.
Best Regards,
8Theme’s Team