>> The most important parts of VSCode are not free software. > What do you mean by this?

The SSH remote connection stuff, the Pylance Python LSP (you are not allowed to use it - the binary - in any other editor but VS Code, not even the OSS Codium) and some other extensions are CSS.

"""Can I load Pylance in Code – OSS? Pylance is licensed for use in Microsoft products and services only, so can only be used on official Microsoft builds of Visual Studio Code and GitHub Codespaces."""

https://github.com/microsoft/pylance-release/blob/main/FAQ.m...

While I agree that that shows MS doesn't really love open source as much as they say they do, I don't think you can really call those "The most important parts of VSCode".

For python development pylance is one of the most important parts.

Perhaps, but VSCode is used for a lot more than just python.

What's stopping you using any other LSP compatible python language server?

Is your argument that if Microsoft develop any programming tool and then allow it to be used via VS Code they must open source it?

Would you place that same requirement on other extensions? (e.g. sonarcloud)

Well there is Pyright by MS (that's what Pylance is based on) and python-language-server by MS - that one has been superseded by Pyright and is deprecated in Code.

https://github.com/microsoft/pyright https://github.com/Microsoft/python-language-server

The only(?) one not by MS is Jedi: https://github.com/pappasam/jedi-language-server

The Microsoft C++ extension is also not fully open source.

Not sure what OP is referring to, but Microsoft has multiple Visual Studio Code extensions (e.g. Remote SSH) that are closed-source and hard-coded not to work with any self-compiled versions of Visual Studio Code.