Microsoft has reached an agreement to buy GitHub, the source repository and collaboration platform, in a deal worth $7.5 billion. The all-stock deal is expected to close by the end of the year, subject to regulatory approval in the US and EU.

Decade-old GitHub is built on Git, the open source version control software originally written by Linux creator Linus Torvalds. Git is a distributed version control system: each developer has their own repository that they make changes to, and these changes can be propagated between repositories to share those changes. GitHub provides a repository hosting service: a place to put those repositories so that other developers can readily access them. Since its inception, it has become a mainstay of the open source world, with countless projects—including Microsoft projects such as the Visual Studio Code text editor and the .NET runtime—using GitHub repositories as a place to publish their code to the world and coordinate collaborative development. In total, some 28 million developers use GitHub, and there are 85 million code repositories.

On top of its core Git foundation, GitHub has built its own workflows ("pull requests") to ease the merging of changes from one repository to another. It also has integrated issue tracking, a Web front-end for browsing repositories, and a marketplace for a wide range of commercial add-ons and extensions.

Microsoft says that it will retain GitHub's status as an "open platform," being free to use for open source projects and agnostic toward programming languages as well as development tools. The company also says that it will beef up GitHub's paid enterprise side by using its own sales and partner channels to sell GitHub's services.

Microsoft and GitHub have been collaborating for some months already. Last year, the two announced that GitHub would support Microsoft's Git virtual file system designed for enormous, enterprise-size repositories, and at its Build developer conference this year, Microsoft said that it was offering integration between its AppCenter mobile testing service and projects hosted on GitHub.

While this is set to be Microsoft's most successful foray into the open source repository hosting world, it isn't the first. The company's in-house service, CodePlex, was shuttered last year, with the advice being to migrate CodePlex projects to GitHub.

The purchase will see some personnel changes at GitHub. Nat Friedman, founder of Xamarin (the open source implementation of .NET that Redmond acquired in 2016) and current Corporate Vice President at Microsoft will become GitHub CEO. GitHub's current CEO and co-founder, Chris Wanstrath, will become a Microsoft technical fellow. Both will report to Scott Guthrie, executive vice president of the Microsoft Cloud + AI group.