To install:
configure
make
as root (or any user with write permissions to $PREFIX)
make install

To launch the program, type 'gsubedit' from the terminal or open it from the
GNOME panel->Programs->Applications

TIP: Open the Gnome Control Center and click on 'mime-types'. Add a new type
(for instance application/x-subtitle) and specify it's extensions (.sub,
.srt). The select "File types and programs" and add gsubedit to the
mime-type for subtitles. 
Now you should be able to click on a .sub/.srt in your file-browser and open
inte with gsubedit!