User installing bash shell
comp.unix.bsd.freebsd is not widely propagated, so you won't
necessarily get much help here.
See http://www.freebsd.org/support.html for better ideas...
[followups redirected accordingly]
It's possible to install it, but you can't get it to be the login
shell. It might be easier to just adapt to the tab-completion in the
FreeBSD /bin/sh, though. It's not *that* much different.
For a private, user-compiled version, it's probably just as easy to
build it directly from the sources.