Revert "Delete child-of-fair-use sentence in section 1."

This reverts commit c2ac8dc3dd555fe8e481e8554385d318cc127bc5.

This is a result of reading Pam Chestek's comment on the mailing list:
https://lists.fedorahosted.org/pipermail/copyleft-next/2013-February/000525.html