I am sorry for the loss of your rabbit after Mindscape shut down the Nabaztag server. But, it is time you resurrect it by using your own home based server. This is possible by using freely available open-source application called OpenNab.
OpenNab is a PHP based proxy framework which can be downloaded from http://opennab.sourceforge.net
The following is the steps for its installation:
1) Install Apache and PHP5. Follow the steps at Apache.org and php.net.