Crate is a database engine that uses Lucene for storage and leverages portions of Elastic for cluster management. It is a NoSQL storage engine that gives you an SQL API (via REST). It does not support JOINs yet but this work is well underway and we expect a release with JOINs soon. We have several customers migrating from MySQL without JOINs (either handling joins in the application layer, using arrays in columns, or denormalizing data). Transactions are not ACID, we fall into the eventually consistent realm. And finally, not all use cases require user/group security, in fact much of the current SQL usage falls into the single user category.

I also agree that our site is not as clear as it needs to be and we're working on it already.