Is it possible to host Zoho on our own server?

Is it possible to host Zoho on our own server?

I checked the FAQ and a few other places, but I can't seem to find anything that says whether Zoho is a system we can host and maintain on our own servers -- only that it can be associated with domain names. It doesn't look like it is (in which case we may gravitate to another service like OpenMind), but I just wanted to check.