From a quick search, a MATLAB student license is $50 (USD, probably), which is less than most textbooks but still not nothing. Whether piracy is justified or not, I just want to point out that this is how they get you. Microsoft gives cheap Office licenses to schools and Adobe turns a blind eye to amateur piracy of Photoshop because they know that getting you comfortable with their software early means you’re more likely to pay to keep using it professionally later. I don’t know if MathWorks had a hand in the MATLAB requirement (I would bet it was just a prof who wants to stick with what they know), but good on you for trying to push for alternatives and testing against Octave.