Power CMS Builder is an extension that installs the Power CMS Solution pack to your dreamweaver site. Yes, the serial is needed for the Power CMS Install to complete, The Power CMS Solution that is installed by Power CMS Builder needs to be activated on the server.
In power CMS, you can create additional Administrator users. If logged in as an administrator, you will not have access to the settings panel, only the Supper Admin has access to the settings panel.
PowerCMS can manage header information, but you will need to create the content areas for this. for each of your content pages, create new content areas named:
meta-title
meta-keywords
meta-description
then apply the developer nots to the title, keywords and description tags on your page.