The database (*.kbd file) can be access from Windows and Linux systems.
Installation on Ubuntu
The Linux port is named KeePassX and has its own webpage.
Unfortunately, the version that will be installed from the applications main menu isn't the newest, so you should add the following repository to get the latest version:
echo "deb http://ppa.launchpad.net/sniperbeamer/ubuntu/ hardy main #SniperBeamer (KeepassX, ...)" > /etc/apt/sources.list.d/sniperbeamer.list
apt-get install keepassx