Purchase a Microsoft® Office SharePoint® Server licence for each server and CALs for either users or devices.
Standard and Enterprise CALs
Microsoft Office SharePoint Server (MOSS) 2007 offers different levels of functionality, and there are CALs which correspond to this. The core functionality is linked to a Standard CAL assigned to a user or device.
If the extended functionality is utilised, then the purchase of an Enterprise CAL is in addition to the Standard CAL. This is an additive CAL
Excel Services allow users to use a web browser to view and interact with Excel on a SharePoint site. To use Excel Services, the user must have both a Standard and an Enterprise CAL for SharePoint Server.
To publish an Excel spreadsheet to a SharePoint site the user must be using Excel from either Microsoft® Office Professional Plus or Microsoft® Office Enterprise, and both SharePoint CALs.
A MOSS server licence allows the running of one physical or virtual instance.