If you use it to keep notes for your university courses, you effectively use it to further a cause which in the future will make you money, yet I’m sure you’d agree that doesn’t fall into ‘commercial use’.
If I use it to organize the research I do - the knowledge of which I then use in a commercial project - does that constitute work use? In my opinion - yes, I get paid to do that research, but it’s knowledge for me, so no, it is not ‘work use’ to me.
Next step - use it for notes specifically for a work project. As long as I am using it for myself and myself only, only sharing snippets of text that have no relevance to obsidian, not work use. Share a canvas created with obsidian? Work use. Share/publish a whole folder/vault as a wiki? Work use.