BSD != Linux, the "core utilities" are a part of the OS, with FreeBSD/OpenBSD & NetBSD the kernel and user lands are developed together..
Which is different from GNU/Linux (
Linux kernel, GNU user land..)...
What you've found in distfiles are 3rd party source archives.
You can browse the FreeBSD source at:
http://www.freebsd.org/cgi/cvsweb.cgi/src/
And download it:
ftp://ftp.freebsd.org/pub/FreeBSD/re...0-RELEASE/src/