diff --git a/COPYING b/COPYING
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+See individual source files for copyright and licensing details, and
+in particular THIRD-PARTY.md for details of third-party libraries used
+or included in this project.
+
+The overall license of pressure-vessel is
+LGPL-2.1-or-later <https://spdx.org/licenses/LGPL-2.1-or-later.html>.
+
+Unit tests, scripts, the build system, etc. are mostly under the
+permissive MIT/X11 license <https://spdx.org/licenses/MIT.html>.
diff --git a/t/COPYING.LGPL-2.1 b/COPYING.LGPL-2.1
similarity index 100%
rename from t/COPYING.LGPL-2.1
rename to COPYING.LGPL-2.1