All in One SEO pack is a Wordpress SEO plugin to automatically optimize your Wordpress blog for search engines. It comes with standard features such as XML Sitemap Support, Automatic Meta tag generation, Google Analytics support etc.
Yes, you can purchase separate subscriptions for each site. However if you bought a Video SEO license before January 7th 2013, you have an unlimited license. Also, if you bought any Agency license before August 12th 2013, you have an unlimited license.WordPress SEO Plugins Yoast SEO