Blender went this route, but they have a paid team and (contrary to the kickstarter page's promise of " our team has a lot of experience with multi-platform development" ) Leadwerks does not.
I've before suggested that He hire an experienced consultant to code the UI in GTK+ (or Qt, wx, etc ) a complete recode is not necessary - between glade and gtkbuilder a reworked UI should be done in no time flat and the consultant could focus on helping josh tie in the code bits that responds to the evens ( showing images/opengl contexts/altering states, etc ).
ofcourse this rests on the silly notion that the editor components is written in C, C++, python or one of the myriad languages that actually have gtkbuilder bindings.