BOL:

SQL Server 2000 Enterprise Edition
Used as a production database server. Supports all features available in SQL Server 2000, and scales to the performance levels required to support the largest Web sites and enterprise online transaction processing (OLTP) and data warehousing systems.

SQL Server 2000 Developer Edition
Used by programmers developing applications that use SQL Server 2000 as their data store. Although the Developer Edition supports all the features of the Enterprise Edition that allow developers to write and test applications that can use the features, the Developer Edition is licensed for use only as a development and test system, not a production server.

Ну и еще разные требования к ОС:

Enterprise Edition
Microsoft Windows NT Server 4.0, Microsoft Windows NT Server Enterprise Edition 4.0, Windows 2000 Server, Windows 2000 Advanced Server, and Windows 2000 Data Center Server.
Note that Microsoft Windows 2000 Server (any version) is required for some SQL Server 2000 features.

Developer Edition
Microsoft Windows NT Workstation 4.0, Windows 2000 Professional, and all other Windows NT and Windows 2000 operating systems.

А вообще см. BOL: SQL Server Architecture -> Implementation Details -> Editions of SQL Server 2000. там усе есть.