I think GP's point was that slint's commercial licensing is less of a minefield than Qt's, and the terms are straightforward and reasonable.

(I haven't verified this; this is just how I read the GP's comment.)

That's a lot more than "seems" if it's GPL. That is "you need to release your source code entirely under GPL if you even link to this"

There are 3 license: 1. GPL 2. Royalty-free (free of charge for desktop) 3. Paid license (which we hope is less constraining than the Qt commercial one)