Windows SharePoint Services (WSS) which was the free version of SharePoint that shipped with Windows Server in the past, is just that, a thing of the past. They’ve replaced WSS with Microsoft SharePoint Foundation Server, which is the foundation for Microsoft SharePoint Server 2010.
There’s also two new products called Windows SharePoint Server for Internet Sites and Windows SharePoint Search Server, but we haven’t heard anything about these yet so far. Licensing is still based on the Standard (Core) and Enterprise models.
One of the big differences between Microsoft SharePoint Foundation Server 2010 and WSS is that WSS installed the Microsoft SQL Desktop Engine (MSDE) which allowed the free version of the database to have large SQL database just like the full blown version. Microsoft Foundation Server 2010 ships with SQL Express so it’s limited to a 4 gig database.