Your question isn’t clear. I’ll take it a hints on what you are trying to ask.
When I started using openSUSE (actually, it was SuSE and openSUSE didn’t yet exist), I used Gnome as the desktop. And Yast looked different from what I now see. When I later switched the KDE desktop (with openSUSE 11.3), I saw Yast looking more like we now see.
At a root command line (“su -” in a konsole), I could do:
to see Yast as I used to see it with Gnome. Or I could use
to see Yast as I see it now.
Actually, you can still do:
but you get a message:
The GTK GUI has been retired, falling back to Qt.
I don’t want to install PulseAudio,
Several years ago, I was often seeing posts complaining about pulseaudio, though it never actually caused problems for me. I am seeing far less complaining these days. Perhaps people have just become more used to it.
I’m not quite sure, but I think it is what lets me have several different windows using sound at the same time. I can be playing music in the background, while playing a game that makes clicks and buzzing sounds.
I never looked into Ruby. As far as I know, it is just another programming language (like FORTRAN or COBOL or C or Pascal or Python). From where it is used, I’m assuming that it is particularly oriented toward programming graphic applications (GUI applications).
In any case, you only need to understand the language if you wish to write software with that language. Otherwise, just use the software and don’t worry about what language it is written in.
Except for Pulseaudio, the components mentioned are installed by default mainly because they have to do with implementing YaST in openSUSE.
GTK before, and now Qt are graphical frameworks, and as nrickert describes, YaST has been written and re-written using both frameworks.
While GTK/Qt are the graphical components used when you view YaST, Ruby is the most used language to provide the functionality of YaST modules.
So, although today YaST only requires Qt and Ruby, gtk may still be there to provide backwards compatibility for anything that still uses it.
As for Pulseaudio,
Audio support in Linux in general has been a big problem throughout Linux history.
Pulseaudio was proposed, and then accepted not that many years ago to try to provide structural order, and in particular modularize sound architecture. Modularization is a benefit to most architectures, it means that pieces can modernize at different rates, standards can be proposed and enforced, and parts can be replaced without re-building the entire system. The benefits in Pulseaudio is as nrickert describes, we see a lot fewer complaints and more working systems today than before Pulseaudio. Still, audio is a very difficult technology so detractors still complain about how enormous and unwieldy, even mysterious at times Pulseaudio is. You can remove Pulseaudio, but all recent audio technology advances are written to it so what would you replace it with?