Go to release 3.15.1 packages page and download carrot2-dcs-3.15.1.zip.
After download completes:-
Extract the archive to some local directory
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Run dcs.cmd (Windows) or dcs.sh (Linux)
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Point your browser to http://localhost:8080 for further instructions
Note: Carrot2 Document Clustering Server requires Java Runtime Environment (version 1.6.0 or later).