Software project licenses are often a combination of several free
and open source software licenses. License expressions - as specified
by SPDX - provide a concise and human readable way to express these
licenses without having to read long license texts, while still
being machine-readable.

License expressions are used by key FOSS projects such as Linux;
several packages ecosystem use them to document package licensing
metadata such as npm and Rubygems; they are important when exchanging
software data (such as with SPDX and SBOM in general) as a way to
express licensing precisely.

license-expression is a comprehensive utility library to parse,
compare, simplify and normalize these license expressions (such as
SPDX license expressions) using boolean logic like in: GPL-2.0-or-later
WITH Classpath-exception-2.0 AND MIT.