The following file adds Japanese language support to reCAPTCHA MediaWiki extension v.1.7[1]. Simply replace the file ReCaptcha.i18n.php in the installation package or copy and paste the Japanese array. You may see the Japanese language support in action at KyotoWiki.
References
After looking over the Mediawiki chat extensions[1] and failing to get any of those for IRC to work in MediaWiki 1.11.0, I grabbed the extension template[2] and created my very first MediaWiki extension.
To get the extension to work, complete the following steps:
Having used the MediaWiki sitemap repair script by Sy[1] for a while, I wanted to post my version of it which adds a submission feature for the generated sitemap. I think I saw some page mention a submission concept while I was researching the matter, so this is not exactly my idea.