Actually, I can also confirm that this is true. I got the same warning. Although I had it installed for over a month, but rarely use it. I decided to give it another try today. And I got the "error" giving me the choice to either buy Professional version or to stop using the software. I tried to submit a bug report and I was told to upgrade to 5.52. I did this and then I was able to use the software again. But I need to make sure of something.....
So NCH should be more forthcoming about the free vs paid limitations of the software. If there are truly no limitations, then the worst should be a nag screen. If there are limitations, then a particular feature should be greyed out or a notification made that the specific software feature is only for paid users. So @N_C_H_josh or others, can you confirm this debutsetup.exe (which I have installed) has no hidden usage limitations?
Thanks.