Sorry you had a bad experience :/ I can somehow see why and I guess I should make it clearer. There's a "Buy" link in the navigation and on the separate download page [1] it says that a license is required.
I just explained why the limit isn't artificial.
But you're right, I'm sure my communication can improve. I've been spending a lot of time on this project so am somewhat "blind" to mistakes. All I can do is listen to the feedback here and improve.
I think the combo of the nag screen and the inability to pay to get rid of it is a big part of the problem. If you're not going to let people buy the software, you shouldn't add a penalty/hurdle/annoyance to their usage.