Ah indeed, I am one of those painful macOS users.. the carelessness with which the mother company changes and/or breaks API's overnight still boggles my mind. It's funny, I have some experience with Swing, from work, and I kind of like it, API-wise, so I toyed with the idea of JNI'ing my way around it... but it seems such a ridiculous thing to do for a super-simple GUI. Plus missing the chance of actually learning a 'native' (native as in code) GUI toolkit. I remember playing with Qt (many) years ago and making a mental note to get back to it but a 2020 revisit turned into an exercise in frustration, couldn't get it to build anything (very likely to blame on my ageing XCode installation rather than the Qt SDK). But as you point out, licensing issues & overall maker's attitude need to be considered too.

The imgui's are quite neat. I like the fact that building one of the demo's (with an impressive array of widgets) sort of 'just worked.' That's impressive, these days!