GNU says: The oldest book that can be distributed freely is ...

The oldest book that can be distributed freely is the Diamond Sutra, published in China in the year 868.

据GNU称，能够自由分发的最古老的书是868年中国出版的《金刚经》。

http://www.gnu.org/doc/doc.html

http://www.bl.uk/collections/treasures/diamond.html