I am of two minds about this. On the one hand, if the software vendor fails to write their software so as to exclude random IPs --- and I'm not sure this is even possible --- then they are putting their free trial "out there" and relying on the honor of users of the free trial to abstain from logging on multiple times. It seems similar to "honor boxes" at roadside produce stands in rural areas --- they can't have someone sitting there all day while people drive by, so they leave the produce out in the open and rely on the customer's honor and integrity to pay for whatever they take, and only to take as much as they've paid for. On the other hand, is it an exact analogy? I don't know.
I use a VPN to be able to access television programming from abroad that is free on their websites, but only intended for domestic consumption (Canada, UK, Poland, etc.) --- I log onto a network in the given country, and thus circuмvent their licensing. I am not depriving anyone of anything, and theoretically, if the programming contains advertising, I could end up buying the products advertised, or at least buying from those companies, the next time I am in those countries.