Is there a way to share the notes of Google Keep between different persons? For example, could I link the notes to the todos of Thunderbird Lightning, or can I share the notes between two different Google Accounts?
Currently there is no way to share notes on Keep in the same way that you can share a document.
However, if your goal is to share notes between a fixed amount of persons (e.g. family members,) you can always create a new Google account, add it to all Android phones that you need to share on, and enable sync of Keep only on that account.
Try Wunderlist, they have a great IOS and Android app that does it. I know some people who use it and they really seem in love with it.
Maybe give ShareNOTZ a try. It lets you share notes, lists, and reminders,and of course it keeps your own notes synchronized between all your devices. Full disclosure: I'm the developer. As such I'd love any feedback you may have. Thanks!