VS Code is a mostly open-source code editor, with proprietary sprinkles on top, and a proprietary extension marketplace.

VS Codium is a fully open-source alternative based on the same codebase.

VSCode is a high-quality product given for free.

Why is VS Code free?

• good for the reputation of Microsoft as open-source player
• developers are more influential in purchasing their digital products and services than before
• the community is building the majority of the the functionality for other languages and non-core features through extensions.
• it is a cornerstone of their recent online IDE (https://vscode.dev
• a close integration of VS Code with other Microsoft products, it can be touted as a feature to hook people in. See Azure extension for VSCode as example. You can see this integration with GitHub too now, if you press . on any page of a repository
• the author guess that "the philosophy is to make tools for devs, and create an “ecosystem” to sell something extra".
• the telemetry from VS Code gives Microsoft insights on trends and helps with product development. It is a marketing tool for them to gather field research.
• private marketplace: VS Code is configured to use the Microsoft VS Code Marketplace. Its Terms of Use restricts access to Microsoft and GitHub products only. There is nothing stopping Microsoft from changing the marketplace's terms and conditions in the future. That's why is so important. Some VS Code extensions needs VSCode: C# language, C++ language, Live Share, Remote Development extension. These extension sends telemetry (no opt-out).

There is then a comparison of both projects.

Some points about open-vsx and codium projects:

• To publish to the Open VSX marketplace has less requirements and steps than Microsoft’s set-up.
• they both have a cli

Switch to VS Codium? Yes if you

• want to use 100% open-source software
• want to run a private extension registry
• want to support a product that minimises telemetry reporting
• are paranoid about some kind of mischief being afoot with Microsof
• can dismiss the private extension of Microsoft listed above. There is some alternative that needs to be tested though.