Relationship editor

Module

cd ~/github/islandora
git clone git://github.com/giancarlobi/islandora_relationship_editor
mv islandora_relationship_editor /usr/share/v2p2demo2.to.cnr.it/sites/all/modules/islandora/

ARC2

cd ~
wget https://codeload.github.com/semsol/arc2/zip/master
mv master arc2.zip
unzip arc2.zip
mv arc2-master arc2
mv arc2 /usr/share/v2p2demo2.to.cnr.it/sites/all/modules/islandora/islandora_relationship_editor/

Enable Islandora Relationship Editor from DRUPAL admin.
Enable “Related objects” block from DRUPAL admin.