CopyMove for SharePoint 2007 requires one server license for each active Web Front-End (WFE) server in a SharePoint farm. That is one license for each WFE that actively serves user requests. SharePoint application servers like a dedicated search indexer does not require a CopyMove license.
Users hitting an unlicensed WFE will receive a license error. For example, applying a two-server CopyMove license to a SharePoint farm with three active WFEs will only yield a license error to users hitting the third WFE. The third WFE is defined as the last one to receive Web requests to any of the installed CopyMove pages.