wxWidgets - wxWidgets: Cross-Platform GUI Library
LabVIEW - LabVIEW offers many of the functions you'd find in a traditional script-based programming language presented in a more intuitive visual interface ideal fo engineering.
Electron - Build cross platform desktop apps with web technologies
itom - itom is an open source software suite for operating measurement systems, laboratory automation and...
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
PyLab_Works - PyLab_Works is a free and open source replacement for LabView + MatLab, written in pure Python.