BFL was moved from its original subversion repository, to the Orocos subversion repository. Because this is a different repository, it is not possible to automatically migrate your checks out copy of BFL. You will need to store the local changes in your copy of the old repository (svn diff), then check out the new BFL trunk (svn co http://svn.mech.kuleuven.be/repos/orocos/trunk/bfl), and finally apply your changes to the new trunk. Also check out the updated installation instructions.