The Current release of Venkman can be found on
Click the one of the links in the install column to install Venkman using XPInstall. These XPIs WILL work in Netscape 7.x!
Note that these installs need to write to your Mozilla install directory, which means you need to have write access to this directory. If you are on a unixish system and installed your browser via your package management system, you'll need to be root.
See http://skillup.jp/venkman/ for Japanese localizations of Venkman and associated documentation.