Microsoft has confirmed it’s bought GitHub for $7.5 billion. It says the platform will remain independent and open, prompting speculation about exactly why it’s made the purchase.

The price, to be paid in Microsoft stock, is considerably more than initial reports suggested, particularly given that GitHub has been far from profitable.

It’s the latest in a string of moves by CEO Satya Nadella that suggest a more positive attitude to open source than his predecessor Steve Ballmer. A Bloomberg report strongly implies that GitHub would have rejected a similar offer in the Ballmer era.

Announcing the move, Microsoft appeared keen to stress that little will change about the site:

GitHub will retain its developer-first ethos and will operate independently to provide an open platform for all developers in all industries. Developers will continue to be able to use the programming languages, tools and operating systems of their choice for their projects — and will still be able to deploy their code to any operating system, any cloud and any device.

What Microsoft actually gets from the deal is something of a mystery. It’s forecasting it will be making money from the site by 2020, though whether that’s viable without changing the ethos of GitHub is questionable.

One theory is that the real value to Microsoft might be in access to the database of GitHub itself – not necessarily in the code, but rather in the ability to see which projects are potential successes that could lead to software that competes with Microsoft. In particular, some users are raising concerns about access to private projects working on code that will eventually be open source but isn’t yet publicly viewable.