The question of how much does WSS or MOSS cost to license is always being asked.  Getting the information is not always that easy either, so I will provide a quick summary and the appropriate links to follow to simplify this.  One thing to highlight is that the licensing and versions of the "MOSS Suite" changed as of April 1, 2009.  What that means is that Forms Server 2007 was discontinued as a standalone product, SharePoint Designer 2007 is free now and PerformancePoint Server 2007 is now included at no cost with MOSS 2007 Enterprise.

The licensing model for WSS 3.0 is different from MOSS 2007.

Windows SharePoint Services 3.0 Licensing

WSS 3.0 "conforms to the Windows Server 2003 licensing model".  What that means is that WSS 3.0 is part of Windows 2003 Server for free.  You have to license Windows 2003 Server properly to use WSS 3.0.  Will your WSS 3.0 site serve as an external facing site, internal for your employees or both?

Microsoft Office SharePoint Server 2007 Licensing
 
MOSS 2007 is licensed separately based on the following versions:


Office SharePoint Server 2007 for Internet Sites (no CALs required)
-This is you external facing site (anonymous)


Office SharePoint Server 2007 (CALs also required)
-This is you intranet site, you have to buy CAL's for each user.   To use MOSS 2007 Enterprise you have to buy both an standard CAL and an enterprise CAL for each user.

Client Access License
Office SharePoint Server 2007 Standard CAL
Office SharePoint Server 2007 Enterprise CAL

The MOSS 2007 search engine is basically Microsoft Search Server 2008 but it is integrated and not a standalone product.  Microsoft Search Server 2008 is available as a standalone product:

Microsoft Search Server 2008 Licensing


Microsoft Search Server 2008 (no CALs required)
Microsoft Search Server 2008 Express (no CALs required)     Free Download

Supplemental Licensing Information for Windows SharePoint Services
http://technet.microsoft.com/en-us/windowsserver/sharepoint/bb684457.aspx

Windows Server 2003 R2 Client Access Licensing Overview
http://www.microsoft.com/windowsserver2003/howtobuy/licensing/caloverview.mspx

Microsoft Office SharePoint Server 2007 and Related Technologies pricing
http://office.microsoft.com/en-us/sharepointserver/FX102176831033.aspx?ofcresset=1
- Always go to the Microsoft site to verify the latest pricing and licensing.