DB2 Express-C

http://www-306.ibm.com/software/data/db2/udb/db2express/download.html

DB2 Express-C is a version of DB2 Universal Database Express Edition (DB2 Express) for the community. DB2 Express-C is a no-charge data server for use in development and deployment of applications including: C/C++, Java, .NET, PHP, and more. DB2 Express-C can be run on up to 2 dual-core CPU servers, with up to 4 GB of memory, any storage system setup and with no restrictions on database size or any other artificial restrictions.

Restrictions:

Maximum processors: 2
Maximum addressable memory: 4GB
Database Partitioning Feature N/A
Connection Concentrator N/A
DB2 Geodetic Extender N/A
Query Patroller N/A
Net Search Extender N/A

Operating Systems

Linux
Windows

DB2 Express extended features not included in DB2 Express-C:

Warehouse Manager tools & servers,
Extender support,
Informix Data Source Replication,
Replication Data Capture,
APPC and Netbios