copyright must be written in English?

[Ryuichi Arafune <arafune@debian.or.jp>]

Hello,

I have one question. 

copyright must be written in English?
if the answer is "yes", why?

It may be necessory to request an upstream author to write copyright
in English may be neseccesory for many non-Japanese Debian-user.  

But on leagal, the translated copyright has no force, I belive.

I think it is enough to write  such a way:

  "This program copyright is written in Japanese.
   And the copyright permits to distribute this
   program as a "main"
	        "contrib"
	        "non-free" "

in README.Debian

Please comment.
					Thank you in advance.

Research Institute of Electrical Communication
Tohoku University
Dr. Ryuichi Arafune
arafune@ushioda.riec.tohoku.ac.jp