Do not expect any visible changes. Windows Server 2008 build 6003 remains functionally identical to 6002. However, under the hood, the shift enables:
This isn’t a separate service pack. It’s an integral patch. Uninstalling KB4489887 will revert you to Build 6002, but that also removes months of other security fixes. Not recommended unless you have a specific compatibility issue. windows server 2008 build 6003
Windows Server 2008 Build 6003 represents the most mature version of the Windows NT 6.0 server line. While casual users might expect "Build 6002" for Service Pack 2, the presence of Build 6003 indicates the inclusion of the Platform Update, offering a bridge between the Vista-era kernel and the Windows 7-era graphical and development technologies. Do not expect any visible changes
While historically stable and capable, the build is now obsolete and should be considered a security risk in any modern production environment due to the cessation of security patching. It’s an integral patch