Commercial license is not required for the plain C# extension, which is distributed under a custom license for extension install[0] and under MIT for source code[1].
The features of DevKit (which is uninstalled on my system) are as follows[2]:
- VS-style solution explorer
- VS-style test explorer
- Intellicode (extra extension that integrates with DevKit)
I don't have use for any of these, preferring folder style navigation and CMD+T/P/etc., and GitHub Copilot autocomplete does way better job for any text than Intellicode. The "intellisense" VS calls it is just a base autocomplete feature in VSC that works for any language provided it has a back-end that integrates through LSP.