how to install kscope in Ubuntu 9.04?

Seems as though you'll need to build it from source. You can get the source code here:
http://kscope.sourceforge.net/dload.shtml

Download it, navigate to the download directory from the terminal and extract the file.

tar xzvf kscope-1.9.4.tar.gz

You need the basic build tools.

sudo apt-get install build-essential

It depends on >Qt 4.4.0 and Qscintilla2, both available in the Jaunty repositories.

I would also install checkinstall, to your package manager can track the package.

sudo install checkinstall

Then

qmake
make
sudo checkinstall

More on compiling from source in Ubuntu.
https://help.ubuntu.com/community/CompilingEasyHowTo

or you can install cscope through synaptic