I'm running a box with Debian squeeze, and I just ran:
sudo aptitude install jython
which ended up installing Python 2.5:
[...]
Linking and byte-compiling packages for runtime python2.5...
Setting up python2.5 (2.5.5-11) ...
Does anyone know why CPython 2.5 is a dependency for Jython 2.5.1+ on Debian squeeze?