> > portable GUI (MS Windows, Linux).
> 
> There're at least two options: 

Um, for the sake of completeness one should not skip over the whole
Library/GUI section in http://www.ruby-lang.org/en/raa.html which contains
in addition to GTK and Tk also Fltk, XForms (Forms), Qt, Xlib (RGUI), KDE. 

	- Aleksi