QOS can be retrieved from SourceForge from the links on the Project Summary page. The most current code is stored in CVS; use the CVS Repository link to find out how to download files from the repository directly.
The Server and Agent are bundled separately so the Agent can be distributed easily to the machines in the network. The Agent reports its version tag to the Server, and the Server supports all versions of the Agent. This way a rolling upgrade does not affect monitoring.