Does DBA/EVO have to be modified in any way if the IP address of its server gets changed?

No, nothing is related to the IP or MAC address with regard to licenses for DBA, Evo or Pervasive.  They can all be installed to as many workstations as you like and the license will limit the number of concurrent users to your license count.  Pervasive 11 server licensing does register key information regarding the server with Pervasive via the internet so if you make changes to your server like adding memory or changing the motherboard, or move to a new server, you need to deactivate the license, make the changes, then reactivate it.