Power CMS Builder and Power CMS 2 are both basically the same.
Power CMS Builder is a Dreamweaver extension that you can use to add the Power CMS 2 solution functionality to your site.
Since Power CMS Builder is an extension, it includes a developers license, meaning you can add it to as many sites as you like.
the Power CMS Solution can be used on one site per license.
Design Extender includes Power CMS Builder.