Microsoft Knowledge Base Article 300496 contains the following summary:

This step-by-step article describes how to install Microsoft Windows Services for UNIX.

Windows Services for UNIX 3.0 provides a full range of cross-platform services that help you integrate Windows into your existing UNIX environments. Because the Interix subsystem technology is built in, Windows Services for UNIX 3.0 provides platform interoperability and application migration components in one fully integrated and supported product from Microsoft.