Perhaps he will, one day, but for now the large staff he has working for him all depend on sales of Mathematica to feed their families. Curating the data sets

Perhaps he will, one day, but for now the large staff he has working for him all depend on sales of Mathematica to feed their families. Curating the data sets behind Wolfram Alpha (and Mathematica) is a hugely labour-intensive endeavour. Mathematica itself depends on a large team of extremely well educated people; the pan-scientific domain expertise is significant in that company. Jeopardising that with a radical change of business model, like open sourcing Mathematica, would not be the choice of a sane businessman.