This page is only tested on Ubuntu Lucid (10.04) 64-bit, as of 11 August 2010.
First, get ready to compile inkscape from source:
sudo apt-get install build-essential autoconf automake intltool libglib2.0-dev libpng12-dev libgc-dev libfreetype6-dev liblcms1-dev libgtkmm-2.4-dev libxslt1-dev libboost-dev libpopt-dev libgsl0-dev libaspell-dev libpoppler-dev libpoppler-glib-dev libgnome-vfsmm-2.6-dev libssl-dev libmagick++9-dev libwpg-dev bzr
Now, get the inkscape source and build it. The bazaar checkout will take several minutes depending on your interwebs, and the build will take a long time as well (25 minutes on my box, an i7 quad @ 2.4 GHz).
mkdir ~/inkscape-kerf cd ~/inkscape-kerf bzr checkout lp:inkscape cd inkscape ./autogen.sh ./configure --prefix=$HOME/inkscape-kerf make
The next steps will make a tweak to inkscape that causes newly created Linked Offsets and Dynamic Offsets to pull their offset size from the value given in the “Steps” tab of the “Inkscape Preferences” dialog (in the File menu). It will always create an outset, which is what you want to create “extra” material for kerf correction. We use 0.707 pixels for our cutter, but the right value will depend on your laser, material, and monitor DPI. Feel free to inspect the patch if you don't trust me :)
wget http://ai.stanford.edu/~mquigley/static/linked_offset_from_preferences.diff patch -p0 < linked_offset_from_preferences.diff make install
Your newly tweaked build of inkscape will now be in $HOME/inkscape-kerf/bin , so to run it just type
~/inkscape-kerf/bin/inkscape
enjoy.
If you want a 5mil kerf correction (for 10-mil cut, as done at, e.g., Pololu), you would want to use 0.48 pixels (assuming 96 DPI, which is pretty common).