Command-line tools in Debian
Reviewing upstream packages to write debian/copyright files is tedious but important manual work. It is done during initial packaging and after every new upstream release.
Making initial copyright file construction and subsequent review/update easier will improve Debian's software quality.
Starting with Stretch (Debian 9) there are significantly improved tools over previous releases to help.
licensecheck from licensecheck (and older versions of devscripts) can scan source code and report found copyright holders and known licenses. Its approach is to detect licenses with a dataset (medium:~200 regexes) of regex patterns and key phrases (parts) and to reassemble these in detected licenses based on rules. In that sense this is somewhat similar to the combined approaches of Fossology/nomos and Ninka (see below for these tools). It also detects copyright statements. It output results in plain text (with customizable delimiter) or a Debian copyright file format. Written in Perl.
licensecheck --check '.*' --recursive --deb-machine --lines 0 *
cme update dpkg-copyright
Usage is detailed in Config::Model wiki
licensecheck --check '.*' --recursive --copyright --deb-fmt --lines 0 * | /usr/lib/cdbs/licensecheck2dep5
license-reconcile compares the existing copyright with the source code and reports discrepancies. Written in Perl, using licensecheck.
debmake -k also compares the existing copyright with the source code and reports discrepancies.
debmake -cc generates a new copyright file from the source code.
decopy is a tool that "automates creating and updating the debian/copyright files." It also "aims to detects as many licenses as possible" which makes it a tool for license detection too. It uses python-debian to handle Debian machine readable copyright files. Its approach to detect licenses is the same as license-checker. Written in Python, using python-debian.
licensee from ruby-licensee checks LICENSE files and returns known license names. This is the tool used by Github to provide a summary license indication on a repository main page. Its approach is to search for typical LICENSE file names or some package manifest (NPM, Bower, Gemfile, etc) and perform an exact or approximate license text matching against the set of common licenses texts as published at https://choosealicense.com (small: ~20). It output results in YAML format. Written in Ruby.
Wrapper for some of the other tools listed here.
check-all-the-things -f copyright
Libraries in Debian
python-debian has support parsing and creating copyright files (and any Debian-style files such as description, control, Sources, Packages, etc.) Written in Python.
Command-line tools not in Debian
LicenseFinder is a tool that "Find licenses for your project's dependencies." It does so by running application-specific package management tools and detecting package manifests to collect license-related metadata (e.g. Gemfile, etc) and detect licensing using regex against a set of common license texts (small: ~20). It output results in CSV, HTML and other report format. Written in Ruby.
Ninka is a "license identification tool for Source Code". Its approach is to detect licenses from text sentences using a dataset of key license sentences (large: ~600) and assemble the results based on the matched sentences. It output results in CSV format. Written in Perl.
ScanCode is a tool "to scan code and detect licenses, copyrights and more". Its approach is to detect licenses using a dataset of plain license texts (large:~1000 texts) and plain text notices (large:~2500 notices and mentions) and finds exact and approximate matches in source and binaries using full text alignments. It also detects copyright statements and collect license metadata from package manifests (e.g Maven, Pypi, etc.). It output results in JSON, HTML or SPDX format. Written in Python.
dlt has support for parsing and creating Debian machine readable copyright files. Written in Python.
jninka is a port from Perl to Java of ninka. Written in Java.
Apache Creadur rat is a "tool to improve accuracy and efficiency when checking releases." . Its goal is to help Apache Foundation projects to comply with the release policy including detecting licenses. Its approach is to use a key sentences dataset (small: ~20). Written in Java.
FOSSology is a open source license compliance software system and toolkit that can (in version 3.1) generate DEP5 copyright files. Its approach is to detect licenses with a either large (large:~2500 regexes) dataset of regex patterns (nomos) or a full string comparison against license full texts (large: ~400 text) (monk). It also detects copyright statements and does also integrate with Ninka (see below). This is a complete database-backed web application with some command line support written in C/C++ with a PHP frontend.
OSLCv3 Open Source License Checker 3.0 is a "risk management tool for analyzing open source software licenses." It detects licenses using key sentences and diffs using a dataset of license texts (small: ~50). It is developed in Java and seems no longer under development since 2009. Written in Java.
Updating debian copyright file with cme by Dominique Dumont
Creating, updating and checking debian/copyright semi-automatically by Petter Reinholdtsen