.NET, JSON, Embedded, Free Commercial-Use data management solution? What to do? [closed]
Fluent NHibernate Automapping on top of SQLite would meet all your requirements except edit #2 - "NoSQL, preferably all data is a JSON document"
It automaps a relational DB schema from your object model...does not use JSON. edit You might be able to save JSON data as BLOB, however. (caveat: I know almost nothing about JSON)
Have you taken a look at the Karvonite Framework? The Karvonite Framework provides a strongly-typed embedded database system that includes a portable library implementation for .NET / Windows Store / Silverlight / Windows Phone / Xbox development. I have only used this for small database implementations but so far it has met every one of my needs.