It is short for VisualSubSync.
In VSS, there are two modes available: the normal mode and the timing mode. Both modes have a different configurable (Edit > Preferences > HotKeys) set of hotkeys. In timing mode you can change (Edit > Preferences > Mouse) the behavior of the mouse to use a SubStation Alpha like mouse mode: Left/right mouse button set start/stop time. You can also use the space key to create or modify (Edit > Preferences > General > Misc) subtitles with just one key by pressing it when subtitle start, then releasing it when subtitle stop.
It's a DirectShow filter (a sort of plugin) that makes it possible to show subtitles when you playback a video file, if you use a compatible player like Windows Media Player or any of a lot of other players. You can download VSFilter here.
The easiest way is to first do the timing for the lyrics, sentence by sentence. Then you separate each syllable by the slash character: '/'. Then select the subtitle, right click on it and choose Create Karaoke. Finally adjust the timing for each syllable starting from the first to the last one. See the links below for a tutorial on karaoke creation.
You need to modify VSFilter configuration, double click on the arrow in the taskbar, go to the Misc tab and uncheck Pre-buffer subpicture.
See this tutorial for more information.
You can write some new tutorials/documentation, translate or help to improve the existing ones. Some flash animated tutorial could be nice also.
Unfortunately VSS is not made to be run on operating system other than Windows. Maybe it would work with Wine but I've not tried it myself.
A better alternative is to use the native application called Subtitle Editor. It has lot's of similar feature with a nice, clean and simple GUI.
You can extract the content of the installer by using 7-zip which is freely available here.
Yes, here is a sample file mixing several langages.
This problem usually happen on Windows 7 (and later) when decoding AAC.
It's seems there is a limitation in the Microsoft audio decoder when used with third party program like VSS.
To fix the problem you can use Win7DSFilterTweaker to set another audio decoder (ffdshow) as the preferred decoder.