Recently released RTM versions of both our SharePoint SDK downloads are available on the Microsoft Download Center!

-       Install the MOSS SDK and ECM Starter Kit

-       Install the WSS SDK and Workflow Starter Kit

 Here is the difference:

 ·         MOSS SDK and ECM Starter Kit

 Combo of the ECM Starter Kit and the MOSS SDK documentation and samples, and also included is WSS and Office Forms Server SDK documentation so you only have to download and install one package.

 ·         Windows SharePoint Services Developer Resources

 If you are only interested in WSS platform development, here WSS SDK documentation is combined with the Workflow Starter Kit.