If the debian stable packages are listed in /etc/apt/sources.list then
you can do

  apt-get install octave/stable

and it should downgrade the octave to the one in stable (should be
octave 2.0).  Of course, when Jan does the next systemimager upgrade
of all the machines, your version of octave will get wiped out!

To find out what octave and related packages are installed on the system,

  dpkg -l 'octave*'

(don't need to be root)

To find out what packages are available in debian that are related to
octave:

  apt-cache search octave