wxWidgets - wxWidgets: Cross-Platform GUI Library
BambooHR - Personalized HR software for SMBs
Electron - Build cross platform desktop apps with web technologies
Built for Teams - Built for Teams is a well-designed, easy-to-use, cloud-based HR product.
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
CharlieHR - Charlie automates many of the administrative headaches you'll experience when scaling a company, so you can spend less time doing admin and more time doing the things you love.