From Kolab Wiki
Currently (as of Kolab 2.04), the included OpenPKG software does not compile correctly with GCC 4, which is shipped with Ubuntu 6.06 When a new Kolab version is released that is based on the OpenPKG 2.5 platform, all should work ok using gcc 4.0, but for now, you'll need gcc 3.3 or gcc 3.4.
So, here is what you should do to get things going:
sudo apt-get install bison flex make shtool g++ g++-3.4 rm /usr/bin/gcc rm /usr/bin/g++ ln -s /usr/bin/gcc-3.4 /usr/bin/gcc ln -s /usr/bin/g++-3.4 /usr/bin/g++
Now it is a simple matter of following the normal installation procedure (See: Source Install Howto)
To localise the web interface :
You need to edit /var/lib/locales/supported.d/local to add line : "fr_FR ISO-8859-1" for french (adapt to your own language). After that do :
A reboot maybe necessary.