Hi Steve,
Thanks for reaching and thanks for your interest in our products! So nice to see our plugin being used in such a project 🙂
Regarding your licensing question, if you purchase the unlimited license you can install the plugin in as many site as you need. But only the license holder (you) will be able to access premium support. While you cannot re-sell the license, you can charge the sub sites a fee or not that’s up to you. If all the site are in the same network, you can buy a Network license instead (which is cheaper).
Please let me know if this answers you question,
Best,
Nico