first of all we need to get the sources from Kolab.

Add the following lines to sources.list or create a new file in sources.list.d
deb-src ./
deb-src ./
Of course it is up to you to switch to 3.1 instead.

Now we have the repos active, add the keys and run an update
wget -qO - | apt-key add -
wget -qO - | apt-key add -
apt-get update
Get the packages to download
wget -O packages.txt
Now download all of them including all dependend libraries
grep Package packages.txt | awk '{print $2}' | sort -u | while read packagename
        apt-get -y source $packagename
        apt-get -y build-dep $packagename
Compile all of them and create the DEBs
ls -ld * | grep '^d' | awk '{print $9}' | while read direc
        cd $direc
        debuild -us -uc -b
        cd ..
Now get out for a coffee break, well should more than one :-)

After 12h (more or less on the Pi) we have to install the following packages:
apt-get install intltool libglib2.0-dev python-icalendar python-nose
Python-Icalendar we created before, so this is a manual install.
Then  we can continue with "pykolab".

When all it's done, create a Packages.gz file to have an easy way to install the packages
dpkg-scanpackages .  | gzip -c9 > Packages.gz
Add this directory now to the sources.list file or create a new file in sources.list.d
deb file:///path/to/DEBS /
Run an apt-get update and now install the packages with apt-get or aptitude or something different.

For the impatient:

Just add
   deb /
to your sources.list and run
   apt-get update
and then install with aptitude the metapackage kolab and solve the dependencies manually because I didn't override the priority in the packages information.