WordPress MU

I'm running OS X Server, 10.4.2 with multiple domains. I have WP on one of the domains, but want to make WP available for all the domains. What's the path for doing this? Where does the MU install reside? In the root documents folder or in each domains folder?
Thanks. I love the SW and hope I can get this going.

has anyone even tested wpmu with OS X Server?

I didn't try to install wpmu on my powermac, and I won't.

about the mulitple domains thing.
as far as I can see from the db-contents it seems that blogs are bounded to a specific domain. so test.AAAA.com should be different from test.BBBB.com
BUT currently the blogs are created with tables like $prefix_$username_... which is quite bad because this doesn't allow to have test.AAA.com and test.BBB.com because both would create the same tables.

blog-aliases would be a solution for that problem, or at least separating the table creation for a blog from the username.

To add another domain take a look into the database, specific the 'site' table, and play around with adding a new entry. don't forget to add a default blog for the new domain too.