Yes See the TikiInstall page I think, we do already have FreeBSD people. Tikiwiki is OS independant. It only requires Apache or IIS, MySQL or another database if you run 1.8, and PHP as per the Installation Requirements there is a link from TikiInstall
An installation of Tiki would need to be in each vhost. A empty installation of 1.7.5 is 17Mb. However this is with the included 500+ avatars that can be removed, and all language translations, which could be removed. Also included are a handful of themes, which again once one is chosen as a based the rest can be removed.
Tiki is one product, there are no optional installation components at Install time. Once installed you can remove those items above
Nothing is optional, When we see something we like, we get it into the CVS and it automatically becomes part of the latest package.