While WSS and MOSS are both pieces of software built by the Microsoft Office team.

Windows SharePoint Services 3.0

• WSS is included as a part of the Windows Server 2003 operating system
• WSS as the underlying platform
• WSS does not have its own licensing model. Instead, the use of WSS is controlled through Windows Server 2003 licenses.
• It has the core document management and collaboration platform features With WSS, the average information user can build web-based business applications without numerous technical resources.

MS Office SharePoint Server 2007

• MOSS is a separate product with its own SKU
• MOSS is a value-added set of components and services that has been built on top of this WSS.
• MOSS has its own licensing model that includes server-side licenses and client access licenses (CALs). The MOSS licensing model is further broken out into a Standard Edition and an Enterprise Edition.
• MOSS 2007, is the nexus of the Microsoft Office system It delivers the robust, enterprise-targeted features of SharePoint Products and Technologies, which accelerate business processes across the intranet, extranet, and Internet.