KDE Screen Ruler is part of the KDE project http://www.kde.org/.
KDE Screen Ruler can be found in the kdegraphics package on ftp://ftp.kde.org/pub/kde/, the main FTP site of the KDE project.
In order to compile and install KDE Screen Ruler on your system, type the following in the base directory of the KDE Screen Ruler distribution:
%
./configure
%
make
%
make install
Since KDE Screen Ruler uses autoconf and automake you should have no trouble compiling it. Should you run into problems please report them to the KDE mailing lists.