Hi,
well, Mathematica is a very sophisticated product and Incan umderstand why they don't give it away for free. Also, there are versions that are basically free. One is on the raspberry Pi; if you take the latest board, you will find anresponsive copy of Mathematica on it. And then there is the Wolfram Cloud, where there is a free tier.
Asking for a free version appears to be like going to a car dealer and saying that you would like the car for free. Saying to strip Mathematica of some functionality is like saying that the car dealer can keep the radio, but should still give you the car.
Cheers,
Marco