To run BrightstarDB on Ubuntu you will need Mono > 3.2.4 installed. Ubuntu 14.10 does come with Mono 3.2.8, but even that is a way behind the current state of Mono development and it is a good idea to instead build and install the latest Mono version. Fortunately, this is not that hard to do. The following procedure will get you up and running with the latest version of Mono (at the time of writing).
# First make sure your base installation is up-to-date
sudo apt-get update
sudo apt-get upgrade
# Install build-essential (may well already be installed, but worth checking)
sudo apt-get install build-essential
# You may want to run the remainder of these commands in a scratch directory
# This grabs the current version of mono (3.12.0)
# Point your browser to http://download.mono-project.com/sources/mono
# to check that it is still the most recent version.
wget http://download.mono-project.com/sources/mono/mono-3.12.0.tar.bz2
tar -xvf mono-3.12.0.tar.bz2
cd mono-3.12.0
./configure --prefix=/usr/local
make
sudo make install
# This should show that you now have the latest version of Mono installed successfully!
mono --version
Once you are done and everything is built and installed you can delete both the downloaded .bz2 package and the source extracted from it.
One thing to note, if you want to automate this process, use sudo apt-get -y instead of
sudo apt-get to automatically accept the changes that the apt-get process makes.