Its close in spirit to DRM: they enforce that if you are using their projects, it is under their legal terms.
Many of their VS Code extensions[0] have license terms which /prohibit/ them from being used in editors that are not Microsoft's VS Code editor, and Microsoft can issue cease-and-desist for violations of this, as well as 'open source forks of VS Code' using their marketplace services.
Microsoft also has a pattern they follow where they publish repositories on GitHub to proclaim they are open source, while actually distributing proprietary binary blobs in them that are fundamental core parts of functionality to the codebase[2][3][4]
Many of their VS Code extensions[0] have license terms which /prohibit/ them from being used in editors that are not Microsoft's VS Code editor, and Microsoft can issue cease-and-desist for violations of this, as well as 'open source forks of VS Code' using their marketplace services.
Microsoft also has a pattern they follow where they publish repositories on GitHub to proclaim they are open source, while actually distributing proprietary binary blobs in them that are fundamental core parts of functionality to the codebase[2][3][4]
[0] https://github.com/microsoft/vscode-cpptools/issues/6388#iss...
[1] https://github.com/microsoft/vscode-cpptools/issues/5784
[2] https://github.com/microsoft/win32metadata/issues/766
[3] https://devlog.hexops.com/2024/building-the-directx-shader-c...
[4] https://github.com/microsoft/Azure-Kinect-Sensor-SDK/issues/...