Here's a 10% clone of Mathematica - https://mathics.org/

Maxima is the clone. I remember using it 20 years ago. very nice.

	▲	zozbot234 2 hours ago \| parent \| next [-]
		It's more like both Mathematica and Maxima are clones of the original MACSYMA.
	▲	pfortuny 2 hours ago \| parent \| prev \| next [-]
		Maxima, despite its shortcomings, is a great tool for symbolic computation.
	▲	Y_Y an hour ago \| parent \| prev [-]
		Maxima is a similar CAS, but it's not a clone of Mathematica like Mathics aims to be.