Database Servers

Firebird

• Open-source spin-off of InterBase
• Mid-range to high-end RDBMS
• IDPL license (Initial Developer's Public License)
  

MaxDB (previously SAP-DB)

• High-end RDBMS
• Like Oracle / DB2
• Dual GPL / proprietary licenses

MySQL

• Low-end to mid-range RDBMS
• Dual GPL / proprietary licenses
  

PostgreSQL (Postgres)

• Mid-range to high-end RDBMS
• BSD license