I currently have four seperate wordpess sites on seperate domains but all on the same webserver. I therefore have four identical copies of wordpress.
I can't figure out from the current documentation - will it be possible using 3.0 to run all four sites from one admin and retain seperate domains? or does it only allow sub-domains.
Incidentally, I use a managed server so I don't have access to apache/php so I can't for example, see httpd.conf etc.,
My 'root' looks like:
-site1
--wp-content
--wp-includes
-site2
--wp-content
--wp-includes
...
-siteX
--wp-content
--wp-includes
It will be possible. But you will need use a plugin, .htaccess, or hosting feature to remap or mirror the urls. I haven't done this yet, so I can't walk you through it.
Read up on how people do this using WordPress MU. It'll be similar or the same for 3.0...