You should check out Mathics; It's a free and open source implementation of the 'Mathematica language' written in Python. Admittedly, there are bugs, and the p

You should check out Mathics; It's a free and open source implementation of the 'Mathematica language' written in Python. Admittedly, there are bugs, and the performance is not as good as Mathematica, but a lot of progress has been made (For example, PyPy compatibility is planed for the upcoming release). Give it some time, and I think (hope) it will grow to fill this niche. Also, The fact that Mathics is open, allows you to extend it (in Python for example) with minimal effort. Disclaimer: I contribute to Mathics development in my free time. We are hoping to get more people involved!