Using MS SQL as back end with latest installer

I am about to do an install and I see in the latest installation guide (version: 1.5) that MS SQL is now supported. There does not seem to be a requirement mentioned in the guide regarding a SQL client.

Do I need to install a SQL client?

Or does it use a jdbc connection with a connection string (my guess)?

No client is required, the application uses its own native jdbc connection as you correctly surmised.