It's not free. Grant money means someone's paid for it (us, taxes). Volunteer is about credit, not fiat, but still costs something (gpl restrictions).

Jupyter is great, it's revolutionized online education for example. But it's not as full featured as Mathematica, and like most Foss projects, slower to fix bugs, aka you get what you pay for. Both have a place unless you have hired, 100% dedicated help on juptyer. This is much like public radio vs corporate. Together they do the market needs.