Hey Felix,
Thank you for reaching out to us!
If you only want to use our plugin on a handful of sub-sites and are willing to perform manual updates, then you can use a Personal license (for 1 sub-site), Business license (for 2-3 sub-sites) or an Agency license (for 4-10 sub-sites).
Please note that if you use a Personal, Business, or Agency License for a site on a Multitsite Network, you may see a Disconnection notice in your account on this site when you log in and go to My Account → License Keys. You can ignore this. We are working to improve this messaging and functionality. Additionally, you may not receive notification that updates are available. When an update is available, you will need to visit My Account » Downloads to manually update the plugin.
You will find more info about this subject here: https://theeventscalendar.com/knowledgebase/multisite-license/
I hope this helps! If you have any other questions at all please feel free to let me know and I’d be happy to help as best I can!
Cheers,
Patricia