When the users select Japanese during the setup stage in JIRA, they see the following text:

The Japanese translation of JIRA is available from <b>ImaHima</b> - an
Atlassian partner.

If you would like to use JIRA in Japanese, please download the Japanese
release of JIRA from the<a
href="http://www.jira-jp.com"><b>ImaHima</b></a> website. Please note
that you will have to acquire a Japanese JIRA license from ImaHima to
run the Japanese release.

Since this URL has been changed, please update the link above to point to http://www.atlassian.jp/support/internationalfaq.html