Not all software sources of posts in mirrors

[ykla]

Hi,
  I found it not all software sources are in mirrors. Many sources need to
download in github.com or it's own websites.
  For example, cd /usr/ports/X11/xorg make fetch-recursive and you will see
many software sources are not downloading from freebsd mirrors.
  In this way, I download sources or kernel sources (SVN) very slow in
China *Mainland* where not have any mirrors so that it usually 4KB/s.
  Do they not in mirrors are because of GNU GPL, MIT or others? Like Gentoo
Linux, all software sources are in his mirrors. So why not let all software
sources of freebsd mirrors? Do our servers can't have enough place to do it?

yours,
ykla