> > There are other cross platform APIs e.g. wxWidgets and Gtk > > There used to be a version of squeak with wx bindings wxSqueak but the > code seems not to be on line now. > > GTK is not a very good choice, it works well on Linux but on MacOS and Windows has many issues and a lot less developers bug fixing.
wxWidgets is a nice GUI API but again it does not come remotely close to the feature set and stability of QT. Some of its areas also are abandoned or very much lagging behind. In my case a big turn off was the outdated python wrappers which sent me directly back to QT. When it comes to guis No1 is Native GUIs , No2 is QT. But QT needs a commercial license for developing pro applications. Its free license is GLP which limits the usage on commercial projects. It does however offer a free LGPL version with more limited features. LGPL allows to close code as long as the code is distributed via dynamically linked libraries. Still it may be tricky to balance on the LGPL without falling down. Which is why many like us prefer MIT over LGPL. There are a ton of open source GUI APIs out there, but most of them are immature, limited or plain abandoned. So you have plenty of choice, but I think you will have little reason to prefer something that is not QT, especially if we are talking about commercial projects that need to run on many platforms.
