Legal Team/License Expression Review 1

Overview

The SPDX Legal group will be holding a special break out session to review a number of software examples where the SPDX licensing syntax (i.e., license list + AND/OR operators) may not be sufficient to represent the licensing terms of the software generally. For instance the group will be looking at the various kinds of special exception terms, the use of the ‘+’ in license names and programs derived from multiple source and library files, where each is potentially under a different license. The group will report back to the Legal and Tech working groups with its findings.

The Problem

SPDX loosely defines a mechanism (e.g., syntactic and semantics) to represent the licensing of various different copyrightable items such as source files, programs, libraries, packages, images, fonts, documentation and so forth. That mechanism consists of:

1. a license list with standard short names (constants/operands)
2. a simple collection of boolean expression operators (e.g., AND and OR). Potential others may be needed (e.g., WITH_EXCEPTION, +)
3. Use of parenthesis to create order of precedence

Some of these components are define in the SPDX spec (e.g. operators) while others are maintained in a license list. What is missing is:

• A formal description of a well through license expression language with more consideration and presentation of how these operators and operands work together to represent the current licensing terms of software. For example, the creation of a single document that presents a holistic overview of the license description mechanism with many examples.
• A disciplined process to test the current constructs of the expression language to ensure they are sufficiently expressive to represent most software licensing situations.