Yes, our Magento 2 marketplace extension will work on your production server (main domain) and your subdomain which can be of the form dev.maindomain.com, staging.maindomain.com, test.maindomain.com and the likes. If your subdomain is of the form qa.test.maindomain.com then, the extension will work on this also. In simple words, we can say that one extension will work for one Magento. If you have multiple Magento installed at your end, then you need to purchase separate licenses.