BTW, the immediate trigger for this was wondering if something GNUStep-like was useful for the Haiku GUI platform. Individuals develop for Haiku, and it runs on a GNUStep-like on Linux/BSD too.
Not NIH, with GTK or KDE or WxWidgets (or Enlightenment of FLTK or JUCE) around. More like, developers having the freedom to write native Haiku apps that could be run on other platforms too.