Reuse, not rework

License Awareness

Highly Reusable Software

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How LIDESC identifies licensing of a file

A "LIDESC stamp" is a specially formatted line (or lines) of text which let LIDESC positively identify the copyright license(s) covering a file. The stamp includes a license text file name and an SHA1 hashcode of the license text. The hashcode is needed to verify that the license text now present in the named file is identical to the one used to create the license stamp.

LIDESC stamps are simple enough to cut and paste and often appear within a source language comment. For example, if a file is covered by the GPL, the LIDESC license stamp is
License text in <librock/license/gpl.txt> librock_LIDESC_HC=63c4046d603e0628fdae5b89c418ed01e4e4fdf1

This identification method is robust and accurate with the important property that it permits copying stamps between files, and stamped files between systems. When other changes are made to the file, the stamp remains intact. Multiple license stamps can appear in a single file when multiple licenses apply. There are ways of embedding stamps in compiled files, libraries, and executables.

Even when the full license text is short enough to appear in a file, including the LIDESC stamp will allow automated scanning, processing, and positive identification.

The web form below generates the simple text form of the stamp for some popular licenses. (Stamps for these and additional licenses are available with the command line version also.)

You can also use this form to report a summary of license requirements based on the symbolic tags.

See the command-line documentation Creating license stamps for files for instructions to use LIDESC with non-text files, or if modifying existing files is not feasible.

See also: License lookup by stamp
Next subject: How LIDESC detects and reports licensing conflicts
Up to: LIDESC: Librock License Awareness System

Librock LIDESC. Software License Analyzer and Compatibility Reporter
Copyright 2001-2002, Forrest J. Cavalier III, Mib Software
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