Hi Demogorgon...welcome to the forum.
I am sorry to say this, but if the developer doesn't offer a lifetime license, there isn't anything we can do to change that.
That said, I checked their website and I don't see where a pro version is mentioned. I do see a plus version, though. Is that the same one you are referring to?
I also do not see where on their site that it mentions that the license is only for 1 year.