This addon is a plugin. You need to extract it to your /plugins folder to install it.
SEOCompanion is your Vanilla Search Engine Optimisation's best friend. Right now, it adds metatags to your header, automatically generated from the tags and title of a discussion, and if none is present, it uses the default (look in the plugin default.php to hardcode them.)
SEOCompanion is trying to be your Vanilla forum Search Engine Optimisation's best friend.
0.2.1 Removed the T() call from the description to make the plugin compatible with Vanilla 2.0.18.
0.2 Addition of default value, to be used when not in a discussion page.
0.1 It only does one thing: it adds a "description" and "keyword" metatags to your header, automatically generated from the title and tags of a discussion. There is only parameter: the maximum number of words the "description" metatag value can have.