I contacted Max Rydahl Andersen, a big contributor of this plugin and thus I managed to find what I was looking for.
There maybe other people searching for old version of org/hibernate/hibernate-tools
Thus, here is the link to the svn repo which can be useful to get older versions :
http://anonsvn.jboss.org/repos/hibernate/tools/branches/Branch_3_2/
(It may save some time to know that the version of hibernate-tools can be found in the "build.xml" file or in the Branch_3_2/src/java/org/hibernate/tool/Version.java
CARRE Nicolas