The single most popular extension for VSCode - the one that adds Python support (https://marketplace.visualstudio.com/items?itemName=ms-pytho...) - is somewhat similar: it was originally written by Don Jayamanne, and later acquired by Microsoft. Although in that case, Don was hired by Microsoft as well, and continued working on it:
Curiously, some bits of code went kinda full circle in the process - vscode-python reused the (open source) Python debugger written at Microsoft for Python Tools for Visual Studio.
Not in that sense. The VSCode extension didn't fork the debugger in question - it took the original code verbatim, and simply wrapped it into a DAP adapter.
Ironically, when we rewrote the Python debugger later, we did the same exact thing with pydevd (https://github.com/fabioz/PyDev.Debugger), and for the same reasons - why reinvent the wheel when you can take an existing one that's already better than anything you have? It's also better for the ecosystem, since improvements all flow upstream.
https://devblogs.microsoft.com/python/don-jayamanne-joins-mi...
This can still be seen on GitHub - if you look closely, the official repo at https://github.com/microsoft/vscode-python is a fork!
Curiously, some bits of code went kinda full circle in the process - vscode-python reused the (open source) Python debugger written at Microsoft for Python Tools for Visual Studio.