"Xdialog is designed to be a drop in replacement for the "dialog" or "cdialog" programs. It converts any terminal based program into a program with an X-windows interface. The dialogs are easier to see and use while adding even more functionalities (e.g. with the treeview, the file selector, the edit box, the range box, the help button/box). Because Xdialog uses GTK+, it will also match your desktop theme."
It's not open source yet, but I am planning on making it so. Watch this space. In the mean time I'm open to feedback and bug reports via GitHub issues.
http://xdialog.free.fr/