Hey Hannes, thanks for getting in touch!
Great question. If you only need the plugin on one sub-site of your network, then a single Personal-level license is just fine. If, however, you would like to install the plugin on multiple sub-sites, then you would need the Multisite-level license instead. Here’s more detailed information on the difference with a Multisite license.
Do i understood it right, that i only get updates for one year?
That’s absolutely correct. A valid license gains you access to both support (on this site) and plugin updates as long as the license is active. Once the license is expired, the plugin will still continue to function, but access to support and future updates will be lost until the license is renewed.
Does this help answer your questions? Please let me know. 🙂
Cheers,
Geoff