Honestly in my opinion, If you're a student, and if you use it for the sake of learning it should be okay. But then, you can still use trial version software for that - that should be perfectly legal.

If you are in need of that specific software but can not afford to purchase polished software, you would still be able to find quality open source software if you look hard enough...

-Edit:

Qn: Would you pay the cost of the software if you start earning - since you've already used it?


Scenario:
If you develop a software spending your time and resources.
Would you feel it is fair for some unknown person, using your software without you knowing about it - regardless of the finances...