wxWidgets - wxWidgets: Cross-Platform GUI Library
8th Wall - Cross-Platform Mobile AR
Electron - Build cross platform desktop apps with web technologies
blippar - Blippar is a revolutionary new image recognition platform that lets you capture a real life image and watch it come to life on your mobile device. Just find images with the blipp logo and unlock a new level of interactivity.
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Vuforia - Leading Augmented Rreality platform.