AWS today announced a new database product that is clearly meant to go after Microsoft’s SQL Server and make it easier — and cheaper — for SQL Server users to migrate to the AWS cloud. The new service is Babelfish for Aurora PostgreSQL. The tagline AWS CEO Andy Jassy used for this service in his re:Invent keynote today is probably telling: “Stop paying for SQL Server licenses you don’t need.” And to show how serious it is about this, the company is even open-sourcing the tool.

What Babelfish does is provide a translation layer for SQL Server’s proprietary SQL dialect (T-SQL) and communications protocol so that businesses can switch to AWS’ Aurora relational database at will (though they’ll still have to migrate their existing data). It provides translations for the dialect, but also SQL commands,  cursors, catalog views, data types, triggers, stored procedures and functions.

The promise here is that companies won’t have to replace their database drivers or rewrite and verify their database requests to make this transition.

“We believe Babelfish stands out because it’s not another migration service, as useful as those can be. Babelfish enables PostgreSQL to understand database requests—both the command and the protocol—from applications written for Microsoft SQL Server without changing libraries, database schema, or SQL statements,” AWS’s Matt Asay writes in today’s announcement. “This means much faster ‘migrations’ with minimal developer effort. It’s also centered on ‘correctness,’ meaning applications designed to use SQL Server functionality will behave the same on PostgreSQL as they would on SQL Server.”

PostgreSQL, AWS rightly points out, is one of the most popular open-source databases in the market today. A lot of companies want to migrate their relational databases to it — or at least use it in conjunction with their existing databases. This new service is going to make that significantly easier.

The open-source Babelfish project will launch in 2021 and will be available on GitHub under the Apache 2.0 license.

“It’s still true that the overwhelming majority of relational databases are on-premise,” AWS CEO Andy Jassy said. “Customers are fed up with and sick of incumbents.” As is tradition at re:Invent, Jassy also got a few swipes at Oracle into his keynote, but the real target of the products the company is launching in the database area today is clearly Microsoft.