On june 2d EMC announced a free developer edition of EMC Documentum Content Server 6.5 which you can download from the ECM Developer Community.
To get you started take a look at the Content Server Developer Edition Install instructions. What’s a little bit weird is that Windows Server 2008 seems to be missing from the list of supported OS – I tried installing it anyway but it failed with this error - DIWAOEMExecuteConfigurationscripts failed - "creating index agent" failed. Runtime execution failed with childprocess
Too bad … time to setup a new blank Windows Server 2003.