CVS was the last official beta release of IVAN before the original dev team ceased development in 2005.
It is very similar to release 0.50, with several minor changes and additions. Note that as an unfinished beta release, it has a few bugs and issues, including an abnormal Valdemar spawn rate and a high starting unarmed combat skill. It can be downloaded here.
The continuation of IVAN, starting with release 0.51, is based on CVS, fixes its many issues and further develops upon it.