VSCode itself, for all the promotional materials about how it's open source, is officially "a distribution of the Code - OSS repository with Microsoft-specific customizations released under a traditional Microsoft product license".
But wait, you might say, it's just like Chrome vs Chromium - so long as we have the OSS edition, it's all good! But, unless you're writing JS or TS, you need extensions to do anything useful. Python is an extension. So is C#, and C++. And all of these are partially closed source - e.g. code completion for all three, or debugging for both C# and C++.
Worse yet, the licenses for those closed source parts specifically prohibit their installation and use in anything other than the official closed source VSCode distro. And this isn't just verbiage - there are actual runtime checks in all these products that block attempts to use them in VSCodium, Cursor etc.
The same goes for the official VSCode extension gallery / marketplace - you can't legally use it from anything other than the official VSCode. Enforcing that is trickier, but even here Microsoft managed to find a way to frustrate its users: it used to be possible to download a .vsix from the Marketplace, but that feature has been removed recently, precisely because people were using that in conjunction with Cursor etc.
Maybe you don't think of it like that, but please remember that, especially with some decisions made in the past months, more and more people are turning away from everything Microsoft.
which ones?