I think of this as another one of those cute toys that JixiPix gives away from time to time. Unfortunately the GOTD team didn't include in the readme.txt file the caveat that you had to keep your browser open after downloading today's offer, and then visit the GOTD key page -- otherwise you won't see the form to fill in your email address. The email you then receive includes a link to the JixiPix store -- you proceed to *buy* the app, with 0 money due. There were lots of complaints in the comments, but I find it hard to fault JixiPix for using their normal process for distributing software keys, rather than coming up with a new system just for GOTD.
Portrait Painter itself just gives you a bunch of presets with different styles of posterization. It's not painting, and AFAIK no one has come up with a convincing method of imitating brush strokes -- they have gotten good OTOH at imitating the physical behavior of paints. Portrait Painter does neither. That's Not to say it can't be useful or fun.
In a bit of a side note, the most realistic imitation paintings I'm aware of use painting apps, where you paint on top of a photo, so you add your own brush strokes. Jessica Johnson [Creators Couture] has created a set of Photoshop brushes that may also do the trick. petapixel[.]com/2020/06/26/these-photoshop-brushes-let-you-turn-photos-into-paintings-stroke-by-stroke/ . While a few other apps offer a *maybe* more detailed version of what Portrait Painter accomplishes, & there are plugins for the GIMP, one of the new neural filters in P/Shop *may* do a better job of it, though again minus the brush strokes. That said, I'm not sure that turning a photo into a painting has ever been that popular -- more of a gee whiz, "I can do that" sort of thing that quickly loses its appeal.
Like other JixiPix apps, once you register the software, registration is removed from the menu, until you restart the app, and it's back. The key is stored in a file -- registering more than once just creates more entries in that file. There are 32-bit & 64-bit versions of the software, but no plugins, so no reason to install both -- I have a 32-bit version of PaintShop Pro for example that I use for scanning, and with JixiPix Spectral Art I installed both versions to get the 32-bit plugin.
Installing Portrait Painter adds the program's folder and an uninstall key to the registry. You also get JixiPixCommon & Portrait Painter folders in Users\ [UserName]\ AppData\ Roaming -- copying the program's folder from my VM, those 2 folders were created as soon as I ran & registered the app.