This is 1 of several questions we need to ask about migrating from Small Business Server 2003 to a standard Domain running 1 server with Server 2012 R2. So please limit your answer to this one specific question:
When adding a member server to SBS2003, what issues are faced? ...things like will SBS2003 have licensing issues and stop running?
Briefly, we do not use some of the SBS2003 subsystems like WSUS, SharePoint, Remote Desktop Services (RRAS), DFS/FRS, and Exchange will move to the cloud.