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.
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.