I'm getting tired of illogical choices when implementing open-source projects.
Project developers providing packages that deploy packaged components whether you already have them already or not.
I posted earlier about a diagram of vtiger's data schema. The actual scheme is referenced at vtiger's wiki.
It is not an ERD (Entity Relationship Diagram) nor is it a Class Model. That's what I was originally looking for since I spend more of time working at the logical or conceptual levels rather than the physical.
Vtiger is an open-source CRM suite, originally forked from SugarCRM due to the commercial activities of the SugarCRM team. Vtiger aims to be open-source, although it does have the possibility of purchasable extensions, much like Joomla. There is a lot of history in the fork, much of it best left alone. The main point to remember is that SugarCRM and Vtiger are released under different licences. You need to check that the functionality you require is available under the licence you wish to use.
Although not listed on the vtiger website, it is possible to install vtiger CRM on Mac OS X. I'll briefly describe the steps I went through to get it to work.
I was curious about the relationships between Contacts, Accounts, Leads and Potentials, so I needed a reverse engineering package.
FabForce Designer was a great little application on Windows and seems to have stagnated a little under MySQL's auspices. It's recently been released for OS X, but the recent release requires 10.5 (Leopard) and I'm still on 10.4 (Tiger).