Do you use any tools to generate the documentation? Also are you planning to make C# bindings?

Yes, sure! Just like everybody, we use Doxygen to generate docs. This is our first experience generating docs for a single project that spans C, C++, Python, Java, and GoLang, so it took some time to get it right. But there is probably no better tool.

As for the C# bindings, it's in our long-term plans, but we would prefer to extend the functionality of Java and GoLang bindings first, then build an SDK for JavaScript, and only then C#. So we are more than open to contributors!

As I understand, the GPU acceleration is private to the UDisk engine implementation. Is there anything like that coming to the open-source part?

Is there support for SQL queries? And which DB's can it be used with?

Not yet. SQL can be seen as a higher-level interface for Analytics, this one is just for the underlying CRUD operations.

It currently supports RocksDB and LevelDB, an in-memory variant, and one proprietary Key-Value store. Those are combined with higher-level logic, like Documents collections. Such combination would produce a competitor to MongoDB. Graph collections will produce a replacement to Neo4J, and so on