The latest release is 0.6.0. QDB is in production at BrandsEye but should be considered beta quality for now.
Install qdb-server-0.6.0.deb. This includes init scripts, creates a qdb user and so on.
Install Java 6, 7 or 8 unpack qdb-server-0.6.0.tgz somewhere and run start.sh (to start QDB in the background) or run.sh to run it in the foreground.