[R-gui] Another R-GUI

This is definitively a different matter!

No, not necessarily.  For example, Delphi can create the dialog box
based on the text representation at run time or at compile time.  At
compile time, all it does is translate the text representation into a
binary equivalent, and include that as a resource in the executable;
when the program starts, the dialog is constructed based on that data.

If you wanted to create it at run-time, you just create the binary
structure in some other way, and then execute the same code to
actually create the dialog.  For example, the IDE of Delphi is written
in Delphi, and that's how it creates the forms at design time.

Well, the difference might not be between creation at run-time or at compile 
time, but there still is an important difference in the level at which the 
GUI is described.
What you're talking about is at a rather low level. It allows for maximum 
control, but it certainly is not something that can easily be shared across 
projects using different toolkits.
What I'm talking about is at a much higher level. It's about using a single 
tag for defining a complex control potentially composed of several 
VB/VC/Qt/GtK/Delphi/whatever-widgets, and it's about describing only a rough 
layout/core functionality. It certainly does not allow for as much control, 
and as mentioned, it might not be suited for all purposes, but it can easily 
be shared across totally different projects. 
BTW, a nice side effect of using a high-level description is that you get a 
consistent look and feel across different dialogs (created by different 
people), and that the description is simple to read and simple to write.

Thomas