For more details, see Microsoft Acquires Citus Data: Creating the World’s Best Postgres Experience Together | Citus Data and Microsoft acquires Citus Data, re-affirming its commitment to Open Source and accelerating Azure PostgreSQL performance and scale | Microsoft Blog; for a history of Postgres and its significance, see Looking Back at Postgres (PDF), a chapter from the recently published Making Databases Work: The Pragmatic Wisdom of Michael Stonebraker
"Microsoft on Thursday said that it's acquiring Citus Data, a start-up that has commercialized open-source database software called PostgreSQL. Terms of the deal weren't disclosed.Microsoft acquires another open-source company, Citus Data | CNBC
The deal could help Microsoft make its argument that it supports open-source technologies, particularly in the cloud, while continuing to make money from popular proprietary software like Windows and Office. In the cloud business, Microsoft wants to use openness as a way to pick up business amid competition from Google, market leader Amazon and others."