1. The X Toolkit ( libXt.so) is a widget library that has always come free with X. It is crude-looking by today's standards. It doesn't feature 3D (shadowed) widgets, although it is comes free with X. [The excellent xfig application, an X Toolkit application, was in fact used to do the diagrams in this book.]Motif ( libM.so) is a modern, full-featured widget library that had become an industry standard. Motif is, however, bloated, slow, and dependent on the X toolkit. It has always been an expensive proprietary library. Tk (tee-kay, libtk.so) is a library that is primarily used with the Tcl scripting language. It was probably the first platform-independent library (running on Windows, all UNIX variants, and the Apple Mac). It is, however, slow and has limited features (this is progressively changing). Both Tcl and Motif are not very elegant-looking. Around 1996, we saw a lot of widget libraries popping up with different licenses. V, xforms, and graphix come to mind. (This was when I started to write coolwidgets--my own widget library.) There was no efficient, multipurpose, Free, and elegant-looking widget library for UNIX. This was a situation that sucked and was retarding Free software development. From Rute-Users-Guide