Install Scripts run fine on FreeBSD, as far as I know. In fact, once installed and all services are configured appropriately Virtualmin Professional runs roughly identically on nearly all platforms.
There are a few caveats on some platforms, and FreeBSD, unfortunately has the most debilitating caveats, I think.
One of them is that FreeBSD only supports 16 secondary groups, so you can’t lock down home directories very tightly (750 permissions are right out), because Apache won’t be able to get to the web content. If you have 15 or fewer virtual servers, you can still use this feature safely, I think. Modern Linux systems support unlimited secondary groups, and so it’s possible to have Apache be a member of all of the virtual server groups–it’s a very elegant way to handle ownership and permissions. There are alternatives on FreeBSD but none are very good…so basically, you just need to make sure virtual server homes have sane permissions within them to limit the risk. Granting only FTP access and chrooting users into their homes is a reasonable option for containing this problem.
Another problem is that FreeBSD, by default, does not support long usernames, so you have to use munged usernames, like joecooper.virtu, instead of joecooper.virtualmin or firstname.lastname@example.org. You have to rebuild the kernel and several system tools to use longer names.
These two issues, plus lack of sane package management, conspire to make FreeBSD impossible to make a “Grade A” supported OS. But, it will be Grade B by the end of the week, I think. The install script is coming along pretty nicely–I’ve got two or three more quirks to work out, and a lot of test iterations, remaining. But I expect it to wrap up soon.
When the script is actually capable of doing an install, even if it’s still fragile, it will be made publicly available. Right now, the testing is of the form: Run it, see where it breaks, fix it, run it again. No sense frustrating folks with a version that we know is broken–wait until it is broken in ways I don’t know about, and then I’ll unleash it on you.