CMS like Joomla can be pretty heavy for server resources and if you don’t update the content it’s reasonable to make it static HTML. Also, hackers and spammers can’t exploit it.
You can use the Httrack for Windows for downloading the entire Joomla website or Wget which is a part of Mac OS, but runs on Windows and Linux too.
For Wget run:
wget --mirror --convert-links --adjust-extension --page-requisites --no-parent http://www.yourdomain.com
After the domain is downloaded you need to rewrite all the links because they will point at …/some-page/index.html. Users and search engines need just …/some-page/.
This solves the Dynamic to Static Kit.