Licensing for DB2 Express C changed in 9.7 version a bit. DB2 Express C is still free to use and distribute, but DB2 Express C FTL - Fixed Term License is no more. FTL licensing option was moved to regular DB2 Express Edition.
This is good move because people sometimes criticised that DB2 Express FTL have more issues than regular express version. Also it will make easier sw maintenance for IBM because they can now concentrate on 3 DB2 Editions (Express, Workgroup, Enterprise). DB2 Pure Scale is more database version (9.8) than edition. DB2 Express C is from IBM side like fire and forget missile, no need to test Fixpacks and bug fixes on it.
By purchasing DB2 Express FTL you will get additional features. CPU and memory limit will be 4 cores / 4 GB RAM total, you can use HADR, homogeneous federation, homogeneous SQL replication, online table reorganization, Tivoli System Automation for Multi-platforms, backup compression and access to past DB2 versions - 9.1 and 9.5. It is system capable of managing 24/7 workloads with medium number of connected users. I heard that it can even handle 500 connected users if their database activity is low, but usually is deployed for 100 or less users.
Price for FTL option is unchanged - US $2,995 per server/1 year and you can buy it here. You will get full 24h technical support and access to Fixpacks. FTL licensing option is often praised because its easy to understand and you can deploy it on any server size.